Exposure apparatus and exposure method, and device manufacturing method

ABSTRACT

In corner sections of first to fourth quadrants whose origin point is a center of an upper surface of a stage, three each of two-dimensional heads are provided. The three each of two-dimensional heads include one first head and two second heads. The stage is driven, while measuring a position of the stage using three first heads that face a two-dimensional grating of a scale plate provided above the stage from the four first heads, and during the driving, difference data of measurement values of the two second heads with respect to the first head in a measurement direction are taken in for head groups to which the three first heads belong, respectively, and using the difference data, grid errors are calibrated.

This is a divisional of application Ser. No. 16/522,716, filed Jul. 26,2019, which is a divisional of application Ser. No. 15/848,615, filedDec. 20, 2017, which is a divisional application of application Ser. No.15/585,866 filed May 3, 2017, which is a divisional application ofapplication Ser. No. 14/432,522 filed Jun. 10, 2015 which is a 371 ofinternational application PCT/JP2013/076820 which claims priority to JP2012-219952. The disclosures of the prior applications are herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to exposure apparatuses and exposuremethods, and device manufacturing methods, and more particularly to anexposure apparatus and an exposure method used in a lithography processfor manufacturing microdevices (electronic devices) such as asemiconductor device, and a device manufacturing method which uses theexposure apparatus or the exposure method.

BACKGROUND ART

Conventionally, in a lithography process to manufacture electronicdevices (microdevices) such as semiconductor devices (integratedcircuits and the like) and liquid crystal display devices, a projectionexposure apparatus of a step-and-repeat method (a so-called stepper), aprojection exposure apparatus of a step-and-scan method (so-calledscanning stepper (also called a scanner)) and the like are mainly used.

In this type of exposure apparatus, along with finer device patterns dueto higher integration of semiconductor devices, requirements for highoverlay accuracy (alignment accuracy) are increasing. Therefore,requirements are increasing for higher accuracy on position measurementof substrates such as a wafer or a glass plate and the like on which apattern is formed.

As a device for satisfying such requirements, for example, in PTL 1, anexposure apparatus is proposed equipped with a position measurementsystem that uses a plurality of encoder type sensors (encoder heads)which are mounted on a substrate table. In this exposure apparatus, theencoder heads measure a position of the substrate table by irradiatingmeasurement beams on a scale which is placed facing the substrate tableand receiving return beams from the scale.

However, as a premise for the exposure apparatus according to PTL 1equipped with the position measurement system to achieve exposure withhigh precision, grating pitch and grating shape of the grating that thescale has are “not to vary at all” for over a long period of time.Further, even if the grid varies, there are no means for monitoring thevariation except for monitoring the variation based on exposure results.

However, when considering that a permissible value of a positioningerror required in a wafer stage of the current exposure apparatus is ata nm level, it is difficult to think that the grid will not vary over along time when viewed at a nm level.

Further, transition from an age of a 300 mm wafer to an age of a 450 mmwafer is near at hand and when it comes to an exposure apparatushandling 450 mm wafers, it is considered that while the wafer stageincreases in size, the permissible value of the positioning error willbecome tighter than the present (or around the same as the currentlevel). Using the position measurement system according to PTL 1described above in the exposure apparatus handling 450 mm wafers withoutany changes is considered to be difficult, when considering a furtherincrease in the size of the scale (grating) that accompanies largerwafers.

A similar problem also occurs in an exposure apparatus disclosed in, forexample, PTL 2 and the like that is equipped with an encoder system.

CITATION LIST Patent Literature

-   [PTL 1] U.S. Patent Application Publication No. 2006/0227309-   [PTL 2] U.S. Patent Application Publication No. 2008/0088843

SUMMARY OF INVENTION Solution to Problem

The present invention was made under the circumstances described above,and according to its first aspect, there is provided a first exposureapparatus which exposes an object with an energy beam and forms apattern on the object, the apparatus comprising: a movable body which ismovable along a plane including a first axis and a second axis that areorthogonal to each other holding the object, a position measurementsystem which has a plurality of heads placed at one of the movable bodyand an outside of the movable body that irradiates a measurement beamfrom a part of the plurality of heads onto a measurement surface placedon an other of the movable body and the outside of the movable body,receives a return beam from the measurement surface, and measurespositional information of the movable body, and a control system whichdrives the movable body based on the positional information, wherein aone-dimensional or a two-dimensional grating is formed on themeasurement surface, the plurality of heads includes a first head groupplaced within a predetermined plane facing the measurement surface thatincludes at least three heads having a measurement direction in at leastone direction of two directions within the predetermined plane and adirection orthogonal to the predetermined plane, and of the at leastthree heads, at least two heads are placed on a same straight linewithin the predetermined plane, and at least one head remaining isplaced at a position different from the straight line within thepredetermined plane, and the at least one head is a reference head usedfor acquiring the positional information, and the at least two heads aremeasurement heads used for measuring a difference of measurement valuesin the measurement direction with respect to measurement values of thereference head.

According to this apparatus, the movable body is driven by the controlsystem, based on positional information obtained by the positionmeasurement system. Further, difference of measurement values in themeasurement direction is measured for at least one reference head andthe remaining at least two measurement heads, respectively, which areused for obtaining the positional information belonging to the firsthead group. This measurement of the difference, by being performedconcurrently with the movement of the movable body, allows variationquantity of the grid in the measurement direction of the measurementsurface to be monitored, based on data of the difference.

According to a second aspect of the present invention, there is provideda second exposure apparatus that exposes an object with an energy beamand forms a pattern on the object, the apparatus comprising: a movablebody which holds the object and is movable along a plane including afirst axis and a second axis which are orthogonal to each other; aposition measurement system which has a plurality of heads placed at oneof the movable body and outside of the movable body that irradiates ameasurement beam from a part of the plurality of heads on a measurementsurface placed at an other of the movable body and the outside of themovable body, receives a return beam from the measurement surface, andmeasures positional information of the movable body; and a controlsystem which drives the movable body based on the positionalinformation, wherein one of a one-dimensional and a two-dimensionalgrating is formed on the measurement surface, and the plurality of headsare placed within a predetermined plane facing the measurement surfaceand includes a head group including at least two heads whose measurementdirections are in at least one direction of at least a first directionand a second direction within the predetermined plane and a directionorthogonal to the predetermined plane, and two of the at least two headsare placed apart in a direction intersecting each axis which are an axisalong the first direction and an axis along the second direction withinthe predetermined plane, and one head of the two heads is a referencehead used for acquiring the positional information, and a remaining onehead of the two heads is a measurement head used for measuring adifference of measurement values in the measurement direction withrespect to measurement values of the reference head.

According to a third aspect of the present invention, there is provideda device manufacturing method comprising: forming a pattern on an objectusing one of the first and the second exposure apparatus describedabove; and developing the object on which the pattern is formed.

According to a fourth aspect of the present invention, there is provideda first exposure method in which an object is exposed with an energybeam and a pattern is formed on the object, the method comprising:irradiating a measurement beam from a part of a plurality of headsplaced on one of a movable body which moves holding the object along aplane including a first axis and a second axis orthogonal to each otherand an outside of the movable body on a measurement surface placed on another of the movable body and the outside of the movable body on which aone-dimensional or a two-dimensional grating is formed, receiving areturn beam from the measurement surface, and measuring positionalinformation of the movable body; and driving the movable body based onthe positional information that has been obtained, wherein, theplurality of heads includes a first head group, placed within apredetermined plane facing the measurement surface, the heads includingat least three heads whose measurement directions are in at least twodirections within the predetermined plane and at least one directionorthogonal to the predetermined plane, and of the at least three heads,at least two heads are placed on a same straight line within thepredetermined plane, and at least a remaining head is placed within thepredetermined plane at a position different from the straight line, andin the driving, the movable body is driven within the predeterminedplane, and concurrently with this driving, difference data ofmeasurement values in the measurement direction of different headsbelonging to the first head group is taken in, and grid errors in themeasurement direction of the measurement surface are calibrated based onthe difference data taken in, the difference data including differencedata of measurement values in the measurement direction, of measurementvalues of a reference head which is the at least one head used formeasuring the positional information and measurement values of eachmeasurement head of the at least two heads, belonging to the first headgroup.

According to this method, the movable body is driven based on thepositional information that has been obtained, and concurrently withmoving the movable body within the predetermined plane, difference datain the measurement direction of different heads belonging to the firstgroup including difference data of measurement values in the measurementdirection of at least one reference head and the remaining at least twomeasurement heads, respectively, which are used for obtaining thepositional information belonging to the first head group are taken in,and based on the difference data which has been taken in, calibration isperformed of grid errors in the measurement direction of the measurementsurface.

According to a fifth aspect of the present invention, there is provideda second exposure method in which an object is exposed with an energybeam and a pattern is formed on the object, the method comprising:irradiating a measurement beam from a part of a plurality of headsplaced on one of a movable body which moves holding the object along aplane including a first axis and a second axis orthogonal to each otherand an outside of the movable body on a measurement surface placed on another of the movable body and the outside of the movable body on which aone-dimensional or a two-dimensional grating is formed, receiving areturn beam from the measurement surface, and measuring positionalinformation of the movable body; and driving the movable body based onthe positional information that has been obtained, wherein, theplurality of heads includes a head group including at least two heads,placed within a predetermined plane facing the measurement surface,whose measurement directions are in at least one direction of at leasttwo directions within the predetermined plane and a direction orthogonalto the predetermined plane, and two heads of the at least two heads areplaced apart in a direction intersecting each axis which are an axisalong the first direction within the predetermined plane and an axisalong the second direction, and in the driving, the movable body isdriven within the predetermined plane, and concurrently with thisdriving, difference data of measurement values in the measurementdirection of different heads belonging to the head group is taken in,and based on the difference data taken in, grid errors in themeasurement direction of the measurement surface are calibrated, thedifference data including difference data of measurement values in themeasurement direction of measurement values of a reference head used formeasuring the positional information which is one head of the two headsbelonging to the head group and measurement values of one head remainingof the two heads.

According to a sixth aspect of the present invention, there is provideda device manufacturing method, comprising: forming a pattern on theobject by one of the first and the second exposure methods describedabove; and developing the object on which the pattern is formed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view that schematically shows a structure of an exposureapparatus related to an embodiment.

FIG. 2 is a view that shows a structure of an encoder system placedaround a projection optical system.

FIG. 3 is a view that shows a structure of an encoder system placedaround an alignment system.

FIG. 4 is a view for explaining an example of a placement of three headsbelonging to a first head group placed at a corner section of a firstquadrant on a wafer table upper surface.

FIG. 5 is an enlarged view of a wafer stage which is partiallyfragmented.

FIG. 6 is a view that shows a placement of encoder heads on the waferstage.

FIG. 7 is a view that shows a placement and a measurement direction ofthe first head group placed at the corner section of the first quadranton the wafer table upper surface.

FIGS. 8A to 8C are views that show a placement and a measurementdirection of a third head group placed at a corner section of a thirdquadrant on the wafer table upper surface, a second head group placed ata corner section of a second quadrant on the wafer table upper surface,and a fourth head group placed at a corner section of a fourth quadranton the wafer table upper surface, respectively.

FIG. 9 is a block diagram that shows a main structure of a controlsystem related to stage control of the exposure apparatus in FIG. 1.

FIG. 10 is a view that shows a relation between a placement of encoderheads and scale plates and measurement areas of an encoder system.

FIGS. 11A and 11B are views that show other placement examples of headsbelonging to each head group.

DESCRIPTION OF EMBODIMENT

Hereinafter, an embodiment of the present invention will be described,based on FIGS. 1 to 10.

FIG. 1 shows a schematic structure of an exposure apparatus 100 relatedto the embodiment. Exposure apparatus 100 is a projection exposureapparatus of a step-and-scan method, or a so-called scanner. As it willbe described later on, a projection optical system PL is provided in thepresent embodiment, and in the description below, the description willbe made with a direction parallel to an optical axis AX of projectionoptical system PL described as a Z-axis direction, a direction in whicha reticle and a wafer are relatively scanned within a plane orthogonalto the Z-axis direction described as a Y-axis direction, a directionorthogonal to the Z-axis and the Y-axis described as an X-axisdirection, and rotation (tilt) directions around the X-axis, the Y-axisand the Z-axis described as a θx direction, a θy direction and a θzdirection, respectively.

Exposure apparatus 100 is equipped with an illumination system 10, areticle stage RST which holds a reticle R, a projection unit PU, a waferstage device 50 including wafer stages WST1, WST2 on which a wafer W ismounted, a control system for these parts and the like.

Illumination system 10 includes a light source, and an illuminationoptical system which has an illuminance equalizing optical systemincluding an optical integrator and the like, a reticle blind and thelike (each of which are not shown), as is disclosed in, for example,U.S. Patent Application Publication No. 2003/0025890 and the like.Illumination system 10 illuminates a slit shaped illumination area IARon reticle R set (limited) by the reticle blind (masking system) withillumination light (exposure light) IL at an almost equal illuminance.Here, as illumination light IL, an ArF excimer laser beam (wavelength193 nm) is used as an example.

On reticle stage RST, reticle R which has a circuit pattern and the likeis formed on its pattern surface (a lower surface in FIG. 1) is fixed,for example, by vacuum chucking. Reticle stage RST is finely drivablewithin an XY plane and is drivable in a scanning direction (the Y-axisdirection which is a direction orthogonal to the page surface in FIG. 1)at a predetermined scanning velocity by a reticle stage driving system11 (not shown in FIG. 1, refer to FIG. 9) that includes, for example, alinear motor and the like.

Positional information (including information on position in the θzdirection (θz rotation quantity)) of reticle stage RST within the XYplane (movement plane) is constantly detected by a reticle laserinterferometer (hereinafter referred to as a “reticle interferometer”)16 shown in FIG. 1 that irradiates a measurement beam on a movablemirror 15 (in practice, a Y movable mirror (or a retroreflector) havinga reflection surface orthogonal to the Y-axis direction and an X movablemirror having a reflection surface orthogonal to the X-axis directionare provided), at a resolution of, for example, around 0.25 nm.Incidentally, to measure positional information of reticle R at least indirections of three degrees of freedom, instead of, or in combinationwith reticle interferometer 16, an encoder system as is disclosed in,for example, U.S. Patent Application Publication No. 2007/0288121 andthe like can be used.

Projection unit PU is placed below reticle stage RST in FIG. 1 (on the−Z side), and is held by a main frame (metrology frame) which structuresa part of a body which is not shown. Projection unit PU has a barrel 40,and projection optical system PL consisting of a plurality of opticalelements held by barrel 40. As projection optical system PL, forexample, a dioptric system is used consisting of a plurality of opticalelements (lens elements) arranged along an optical axis AX parallel tothe Z-axis direction. Projection optical system PL, for example, isdouble telecentric, and has a predetermined projection magnification(such as, for example, ¼ times, ⅕ times or ⅛ times). Therefore, whenillumination area IAR is illuminated by illumination light IL fromillumination system 10, by illumination light IL which has passedreticle R which is placed so that its pattern surface almost coincideswith a first plane (an object plane) of projection optical system PL, areduced image of a circuit pattern of reticle R within illumination areaIAR (a reduced image of a part of the circuit pattern) is formed viaprojection optical system PL, on an area (exposure area) IA conjugatewith illumination area IAR on wafer W which has its surface coated witha resist (a sensitive agent) that is placed on a second plane (imageplane) side of projection optical system PL. Then, by synchronousdriving of reticle stage RST and wafer stage WST1 or WST2, scanningexposure of one shot area (divided area) on wafer W is performed and thepattern of reticle R is transferred on the shot area, with reticle Rbeing relatively moved in the scanning direction (the Y-axis direction)with respect to illumination area IAR (illumination light IL) whilewafer W is relatively moved in the scanning direction (the Y-axisdirection) with respect to exposure area IA (illumination light IL).That is, in the present embodiment, the pattern of reticle R isgenerated on wafer W by illumination system 10 and projection opticalsystem PL, and the pattern is formed on wafer W by exposing a sensitivelayer (a resist layer) on wafer W by illumination light IL.

Incidentally, the main frame can either be of a conventional gate type,or a suspension support type as is disclosed in, for example, U.S.Patent Application Publication No. 2008/0068568 and the like.

In the periphery of a −Z side edge of barrel 40, a scale plate 21 isplaced parallel to the XY plane, for example, at a height substantiallyflush with the lower end surface of barrel 40. Scale plate 21 in thepresent embodiment as is shown in FIG. 2 is structured, for example,from four L-shaped sections (components) 21 ₁, 21 ₂, 21 ₃ and 21 ₄, andin the center, for example, a rectangular-shaped opening 21 a is formedinto which the −Z side end of barrel 40 is inserted. Here, the width ofscale plate 21 in the X-axis direction and in the Y-axis direction are aand b, respectively, and the width of opening 21 a in the X-axisdirection and in the Y-axis direction are ai and bi, respectively.

At a position spaced apart from scale plate 21 in the +X direction, asis shown in FIG. 1, a scale plate 22 is placed substantially flush withscale plate 21. Scale plate 22, as is shown in FIG. 3, is alsostructured, for example, from four L-shaped sections (components) 22 ₁,22 ₂, 22 ₃ and 22 ₄, and in the center, for example, arectangular-shaped opening 22 a is formed into which the −Z side end ofan alignment system ALG which will be described later is inserted. Thewidth of scale plate 22 is a in the X-axis direction and is b in theY-axis direction, respectively, and the width of opening 22 a is ai inthe X-axis direction and is bi in the Y-axis direction, respectively.Incidentally, in the present embodiment, while the width of scale plates21, 22 and the width of openings 21 a, 22 a were the same in the X-axisand the Y-axis directions, respectively, the width does not necessarilyhave to be the same, and the width can be different in at least one ofthe X-axis and the Y-axis directions.

In the present embodiment, scale plates 21, 22 are supported in asuspended manner by the main frame (metrology frame) which is not shownsupporting projection unit PU and alignment system ALG. On a lowersurface (−Z side surface) of scale plates 21, 22, a reflection typetwo-dimensional grating RG (refer to FIGS. 2, 3 and 5) is formed,consisting of a grating that has a predetermined pitch of, for example,1 μm having a periodic direction in a −45 degrees direction (a −135degrees direction when the Y-axis serves as a reference) with the X-axisserving as a reference, and a grating that has a predetermined pitch of,for example, 1 μm having a periodic direction in a 45 degrees direction(a −45 degrees direction when the Y-axis serves as a reference) with theX-axis serving as a reference. However, due to the structure oftwo-dimensional grating RG and encoder heads to be described later on, anon-effective area of a width t is included in each of the vicinity ofthe outer periphery of each of sections 21 ₁ to 21 ₄, 22 ₁ to 22 ₄structuring scale plates 21, 22. Two-dimensional grating RG of scaleplates 21, 22 covers at least a movement range of wafer stages WST1,WST2 at the time of exposure operation and at the time of alignment(measurement), respectively.

Wafer stage device 50, as is shown in FIG. 1, is equipped with a stagebase 12 supported substantially horizontal on a floor surface by aplurality of (for example, three or four) vibration-proof mechanisms(omitted in drawings), wafer stages WST1, WST2 placed on stage base 12,a wafer stage driving system 27 (only a part of the system is shown inFIG. 1, refer to FIG. 9) for driving wafer stages WST1, WST2, and ameasurement system and the like which measures a position of waferstages WST1, WST2. The measurement system is equipped with encodersystems 70, 71 and a wafer laser interferometer system (hereinaftershortly referred to as wafer interferometer system) 18 and the likeshown in FIG. 9. Incidentally, encoder systems 70, 71 and waferinterferometer system 18 will be described furthermore later in thedescription. However, in the present embodiment, wafer interferometersystem 18 does not necessarily have to be provided.

Stage base 12, as is shown in FIG. 1, is made up of a member that has aplate-like outer shape, and its upper surface is finished to a highflatness and serves as a guide surface when wafer stages WST1, WST2move. Inside stage base 12, a coil unit is housed that includes aplurality of coils 14 a placed in a shape of a matrix with an XYtwo-dimensional direction serving as a row direction and a columndirection.

Incidentally, another base member can be provided to support stage base12 in a levitated manner separately so that stage base 12 functions as acounter mass (reaction force canceller) which moves according to themomentum conservation law by an action of a reaction force of thedriving force of wafer stages WST1, WST2.

Wafer stage WST1, as is shown in FIG. 1, has a stage main section 91,and a wafer table WTB1 which is placed above stage main section 91 andis supported in a non-contact manner with respect to stage main section91 by a Z tilt driving mechanism 32 a (not shown in FIG. 1, refer toFIG. 9). Similarly, wafer stage WST2, as is shown in FIG. 1, has stagemain section 91, and a wafer table WTB2 which is placed above stage mainsection 91 and is supported in a non-contact manner with respect tostage main section 91 by a Z tilt driving mechanism 32 b (not shown inFIG. 1, refer to FIG. 9).

In the present embodiment, because wafer stage WST2 and wafer stage WST1are structured similarly, hereinafter, wafer stage WST1 will bediscussed and described representatively.

Wafer table WTB1 is supported in a non-contact manner by Z tilt drivingmechanism 32 a by adjusting a balance of an upward force (repulsiveforce) such as an electromagnetic force and a downward force (agravitational force) including self-weight at three points, and isfinely driven at least in directions of three degrees of freedom whichare the Z-axis direction, the θx direction, and the θy direction. Aslider section 91 a is provided at a bottom section of stage mainsection 91. Slider section 91 a has a magnet unit consisting of aplurality of magnets having an XY two-dimensional arrangement within theXY plane, a housing which houses the magnet unit, and a plurality of airbearings provided at a periphery of a bottom surface of the housing. Themagnet unit structures a planar motor 30 along with the coil unitpreviously described that performs an electromagnetic force (Lorentzforce) drive as is disclosed in, for example, U.S. Pat. No. 5,196,745and the like. Incidentally, as planar motor 30, the motor is not limitedto a planar motor of the Lorentz force driving method, and a planarmotor of a variable magneto-resistance driving method can also be used.

Wafer stage WST1 is supported in a levitated manner by a predeterminedclearance (clearance/spacing/void (gap)/spatial distance) on stage base,for example, via a clearance of around several μm by the plurality ofair bearings described above, and is driven in the X-axis direction, theY-axis direction and the θz direction by planar motor 30. Accordingly,wafer table WTB1 (wafer W) can be driven in directions of six degrees offreedom (the X-axis direction, the Y-axis direction, the Z-axisdirection, the θx direction, θy direction and the θz direction(hereinafter shortly described as X, Y, Z, θx, θy, and θz)) with respectto stage base 12.

Magnitude and direction of the electric current supplied to each coil 14a structuring the coil unit is controlled by a main controller 20. Inthe present embodiment, as is shown in FIG. 9, wafer stage drivingsystem 27 is structured including a pair of planar motors 30 having acommon stator (coil unit) which drives each of wafer stages WST1 andWST2, and Z tilt driving mechanisms 32 a, 32 b that wafer stages WST1and WST2 are equipped with, respectively. Incidentally, planar motor 30is not limited to a motor of a moving magnet method, and can also be amotor of a moving coil method. Further, as planar motor 30, a planarmotor of a magnetic levitation method can also be used. In this case,the air bearings previously described do not have to be provided.Further, wafer stage WST1 can be driven in directions of six degrees offreedom by planar motor 30. Further, wafer table WTB1 can be finelydriven in at least one direction of the X-axis direction, the Y-axisdirection, and the θz direction. That is, wafer stage WST1 can bestructured by a coarse/fine movement stage.

On wafer table WTB1, wafer W is mounted via a wafer holder which is notshown, and is fixed by a chuck mechanism which is not shown, forexample, by vacuum chucking (or electrostatic suction). Although it isomitted in the drawings, on wafer table WTB1, one or a plurality ofreference mark members is provided on which a plurality of referencemarks such as a pair of first reference marks and a second referencemark are formed that are detected by a pair of reticle alignment systems13A, 13B and alignment system ALG, respectively.

Encoder systems 70, 71 obtain (measure) positional information of wafertables WTB1, WTB2 in directions of six degrees of freedom (X, Y, Z, θx,θy, θz) in a movement area at the time of exposure including an areadirectly below projection optical system PL and a movement area at thetime of measurement including an area directly below alignment systemALG, respectively. Here, a structure and the like of encoder systems 70,71 will be described in detail. Incidentally, movement area at the timeof exposure (a first movement area) is an area in which the wafer stageis moved during an exposure operation within an exposure station (afirst area) where exposure of the wafer is performed via projectionoptical system PL, and the exposure operation, for example, is not onlyexposure of all shot areas on the wafer onto which the pattern should betransferred, but also includes preparatory operations for the exposure(for example, detection of reference marks previously described) and thelike. Movement area at the time of measurement (a second movement area)is an area in which the wafer stage is moved during a measurementoperation within a measurement station (a second area) where measurementof the positional information is performed by detection of alignmentmarks of the wafer by alignment system ALG, and the measurementoperation, for example, is not only detection of a plurality ofalignment marks on the wafer, but also includes detection of referencemarks by alignment system ALG (furthermore, measurement of positionalinformation (height difference information) of the wafer in the Z-axisdirection) and the like.

In wafer tables WTB1, WTB2, as is shown in the planar view in FIGS. 2and 3, with a center of the upper surface serving as an origin point(coincides with the center of wafer W), a first encoder head group 61 ₁,a second encoder head group 61 ₂, a third encoder head group 61 ₃, and afourth encoder head group 61 ₄ are placed in a part of each corner of afirst quadrant, a second quadrant, a third quadrant and a fourthquadrant. Incidentally, in the following description, the encoder headgroup will be shortly described as a head group. The first head group 61₁ includes three encoder heads (hereinafter appropriately referred to asheads) 60 ₁, 60 _(1a), 60 _(1b) placed in the corner section at the +Xside and the +Y side on the upper surface of wafer tables WTB1, WTB2.The three heads 60 ₁, 60 _(1a), 60 _(1b) in the present embodiment areplaced at each apex position of a right triangle. To be more specific,head 60 ₁ is provided at the vicinity of the corner (apex) at the +Xside and the +Y side on the upper surface of wafer tables WTB1, WTB2.Head 60 _(1a), as is shown enlarged in FIG. 4, is placed at a pointshifted by Δx in a −X direction from an installation position of head 60₁. Further, head 60 _(1b) is placed at a point shifted by Δy in a −Ydirection from an installation position of head 60 ₁.

Referring back to FIG. 2 (or FIG. 3), the second head group 61 ₂includes three heads 60 ₂, 60 _(2a), 60 _(2b) placed in the cornersection at the −X side and the +Y side on the upper surface of wafertables WTB1, WTB2. The three heads 60 ₂, 60 _(2a), 60 _(2b) in thepresent embodiment are provided in an arrangement symmetrical to thethree heads 60 ₁, 60 _(1a), 60 _(1b) on wafer tables WTB1, WTB2, withrespect to a straight line (center line) parallel to the Y-axis thatpasses through the center of the upper surface (the origin pointdescribed above).

The third head group 61 ₃ includes three heads 60 ₃, 60 _(3a), 60 _(3b)placed in the corner section at the −X side and the −Y side on the upperside of wafer tables WTB1, WTB2. The three heads 60 ₃, 60 _(3a), 60_(3b) in the present embodiment are provided in an arrangementsymmetrical (point symmetric) to the three heads 60 ₁, 60 _(1a), 60_(1b) on wafer tables WTB1, WTB2, with respect to the center of theupper surface.

The fourth head group 61 ₄ includes three heads 60 ₄, 60 _(4a), 60 _(4b)placed in the corner section at the +X side and the −Y side on the uppersurface of wafer table WTB1, WTB2. The three heads 60 ₄, 60 _(4a), 60_(4b) in the present embodiment are provided in an arrangementsymmetrical to the three heads 60 ₁, 60 _(1a), 60 _(1b) on wafer tablesWTB1, WTB2, with respect to a straight line (center line) parallel tothe X-axis that passes through the center of the upper surface.

As is shown in FIG. 2, a separation distance between heads 60 ₁ and 60 ₂in the X-axis direction and the separation distance between heads 60 ₃and 60 ₄ in the X-axis direction are equally A. Further, a separationdistance between heads 60 ₁, 60 ₄ in the Y-axis direction and theseparation distance between heads 60 ₂ and 60 ₃ in the Y-axis directionare equally B. These separation distances A, B are larger than widthsai, bi of opening 21 a of scale plate 21. In a precise sense, A≥ai+2t,B≥bi+2t, taking into consideration width t of the non-effective areapreviously described. Each of head 60 ₁ to 60 ₄, 60 _(1a) to 60 _(4a),and 60 _(1b) to 60 _(4b), as is shown representatively taking up head 60₁ in FIG. 5, are each housed inside holes of a predetermined depth inthe Z-axis direction formed in wafer tables WTB1, WTB2.

Heads 60 ₁, 60 _(1a), 60 _(1b) belonging to the first head group 61 ₁,as is shown in FIGS. 6 and 7, are two-dimensional heads whosemeasurement directions are in a direction of 135 degrees (−45 degrees)with the X-axis as a reference and in the Z-axis direction. Similarly,heads 60 ₃, 60 _(3a), 60 _(3b) belonging to the third head group 61 ₃,as is shown in FIGS. 6 and 8A, are two-dimensional heads whosemeasurement directions are in the direction of 135 degrees (−45 degrees)with the X-axis as a reference and in the Z-axis direction.

Heads 60 ₂, 60 _(2a), 60 _(2b) belonging to the second head group 61 ₂,as is shown in FIGS. 6 and 8B, are two-dimensional heads whosemeasurement directions are in a direction of 45 degrees (−135 degrees)with the X-axis as a reference and in the Z-axis direction. Similarly,heads 60 ₄, 60 _(4a), 60 _(4b) belonging to the fourth head group 61 ₄,as is shown in FIGS. 6 and 8C, are two-dimensional heads whosemeasurement directions are in the direction of 45 degrees (−135 degrees)with the X-axis as a reference and in the Z-axis direction.

Heads (60 ₁, 60 _(1a), 60 _(1b)) belonging to the first head group 61 ₁,heads (60 ₂, 60 _(2a), 60 _(2b)) belonging to the second head group 61₂, heads (60 ₃, 60 _(3a), 60 _(3b)) belonging to the third head group 61₃, and heads (60 ₄, 60 _(4a), 60 _(4b)) belonging to the fourth headgroup 61 ₄, as is obvious from FIGS. 2 and 5, respectively measurepositional information of wafer tables WTB1, WTB2 (wafer stages WST1,WST2) in each measurement direction by respectively irradiating ameasurement beam (refer to reference code MB in FIG. 5) ontwo-dimensional grating RG formed on the surface of sections 21 ₁, 21 ₂,21 ₃, 21 ₄ of scale plate 21, or sections 22 ₁, 22 ₂, 22 ₃, 22 ₄ ofscale plate 22 opposing the heads, and receiving reflection/diffractionbeams from two-dimensional grating RG. Here, as each of the heads 60 ₁,60 _(1a), 60 _(1b), 60 ₂, 60 _(2a), 60 _(2b), 60 ₃, 60 _(3a), 60 _(3b),60 ₄, 60 _(4a) and 60 _(4b), a sensor head having a structure similar toa displacement measurement sensor head disclosed in, for example, U.S.Pat. No. 7,561,280 can be used.

In the respective heads 60 ₁, 60 _(1a), 60 _(1b), 60 ₂, 60 _(2a), 60_(2b), 60 ₃, 60 _(3a), 60 _(3b), 60 ₄, 60 _(4a) and 60 _(4b) structuredin the manner described above, influence of air fluctuation can bealmost ignored because the optical path length of the measurement beamin the air is extremely short. However, in the present embodiment, thelight source and the photodetector are provided external to each head,or to be more specific, provided inside (or outside) stage main section91, and only the optical system is provided inside each head. Then, thelight source, the photodetector and the optical system are opticallyconnected via an optical fiber which is not shown. To improvepositioning accuracy of wafer table WTB1 (or WTB2), aerial transmissionof laser beams and the like can be performed between stage main section91 and wafer table WTB1 (or WTB2).

When wafer stages WST1, WST2 are positioned within the movement area atthe time of exposure previously described, heads 60 ₁, 60 _(1a), 60_(1b) belonging to the first head group 61 ₁ structure two-dimensionalencoders 70 ₁, 70 _(1a), 70 _(1b), and 71 ₁, 71 _(1a), 71 _(1b) (referto FIG. 9) that irradiate measurement beams (measurement light) on(section 21 ₁ of) scale plate 21, receive diffraction beams from agrating formed on a surface (lower surface) of scale plate 21 having aperiodic direction in a direction of 135 degrees with the X-axis servingas a reference, that is, a direction of −45 degrees with the X-axisserving as a reference (hereinafter appropriately referred to as a −45degrees direction or an a direction), and measure the position of wafertables WTB1, WTB2 in the −45 degrees direction (α direction) and theZ-axis direction.

When wafer stages WST1, WST2 are positioned within the movement area atthe time of exposure previously described, heads 60 ₂, 60 _(2a), 60_(2b) belonging to the second head group 61 ₂ structure two-dimensionalencoder 70 ₂, 70 _(2a), 70 _(2b), and 71 ₂, 71 _(2a), 71 _(2b) (refer toFIG. 9) that irradiate measurement beams (measurement light) on (section21 ₂ of) scale plate 21, receive diffraction beams from a grating formedon a surface (lower surface) of scale plate 21 having a periodicdirection in a direction of −135 degrees with the X-axis serving as areference, that is, a direction of 45 degrees with the X-axis serving asa reference (hereinafter appropriately referred to as a 45 degreesdirection or a (3 direction), and measure the position of wafer tablesWTB1, WTB2 in the 45 degrees direction (β direction) and the Z-axisdirection.

When wafer stages WST1, WST2 are positioned within the movement area atthe time of exposure previously described, heads 60 ₃, 60 _(3a), 60_(3b) belonging to the third head group 61 ₃ structure two-dimensionalencoders 70 ₃, 70 _(3a), 70 _(3b), and 71 ₃, 71 _(3a), 71 _(3b) (referto FIG. 9) that irradiate measurement beams (measurement light) on(section 21 ₃ of) scale plate 21, receive diffraction beams from agrating formed on a surface (lower surface) of scale plate 21 having aperiodic direction in the −45 degrees direction (α direction), andmeasure the position of wafer tables WTB1, WTB2 in the −45 degreesdirection (α direction) and the Z-axis direction.

When wafer stages WST1, WST2 are positioned within the movement area atthe time of exposure previously described, heads 60 ₄, 60 _(4a), 60_(4b) belonging to the fourth head group 61 ₄ structure two-dimensionalencoders 70 ₄, 70 _(4a), 70 _(4b), and 71 ₄, 71 _(4a), 71 _(4b) (referto FIG. 9) that irradiate measurement beams (measurement light) on(section 21 ₄ of) scale plate 21, receive diffraction beams from agrating formed on a surface (lower surface) of scale plate 21 having aperiodic direction in the 45 degrees direction (β direction), andmeasure the position of wafer tables WTB1, WTB2 in the 45 degreesdirection (β direction) and the Z-axis direction.

Further, when wafer stages WST1, WST2 are positioned within the movementarea at the time of measurement previously described, heads 60 ₁, 60_(1a), 60 _(1b) belonging to the first head group 61 ₁ structuretwo-dimensional encoders 70 ₁, 70 _(1a), 70 _(1b), and 71 ₁, 71 _(1a),71 _(1b) (refer to FIG. 9) that irradiate measurement beams (measurementlight) on (section 22 ₁ of) scale plate 22, receive diffraction beamsfrom a grating formed on a surface (lower surface) of scale plate 22having a periodic direction in the −45 degrees direction (α direction),and measure the position of wafer tables WTB1, WTB2 in the −45 degreesdirection (α direction) and the Z-axis direction.

When wafer stages WST1, WST2 are positioned within the movement area atthe time of measurement previously described, heads 60 ₂, 60 _(2a), 60_(2b) belonging to the second head group 61 ₂ structure two-dimensionalencoders 70 ₂, 70 _(2a), 70 _(2b), and 71 ₂, 71 _(2a), 71 _(2b) (referto FIG. 9) that irradiate measurement beams (measurement light) on(section 22 ₂ of) scale plate 22, receive diffraction beams from agrating formed on a surface (lower surface) of scale plate 22 having aperiodic direction in the 45 degrees direction (β direction), andmeasure the position of wafer tables WTB1, WTB2 in the 45 degreesdirection ((3 direction) and the Z-axis direction.

When wafer stages WST1, WST2 are positioned within the movement area atthe time of measurement previously described, heads 60 ₃, 60 _(3a), 60_(3b) belonging to the third head group 61 ₃ structure two-dimensionalencoders 70 ₃, 70 _(3a), 70 _(3b), and 71 ₃, 71 _(3a), 71 _(3b) (referto FIG. 9) that irradiate measurement beams (measurement light) on(section 22 ₃ of) scale plate 22, receive diffraction beams from agrating formed on a surface (lower surface) of scale plate 22 having aperiodic direction in the −45 degrees direction (α direction), andmeasure the position of wafer tables WTB1, WTB2 in the −45 degreesdirection (α direction) and the Z-axis direction.

When wafer stages WST1, WST2 are positioned within the movement area atthe time of measurement previously described, heads 60 ₄, 60 _(4a), 60_(4b) belonging to the fourth head group 61 ₄ structure two-dimensionalencoders 70 ₄, 70 _(4a), 70 _(4b), and 71 ₄, 71 _(4a), 71 _(4b) (referto FIG. 9) that irradiate measurement beams (measurement light) on(section 22 ₄ of) scale plate 22, receive diffraction beams from agrating formed on a surface (lower surface) of scale plate 22 having aperiodic direction in the 45 degrees direction (β direction), andmeasure the position of wafer tables WTB1, WTB2 in the 45 degreesdirection ((3 direction) and the Z-axis direction.

As it can be seen from the description above, in the present embodiment,regardless of irradiating the measurement beam (measurement light) oneither one of scale plates 21, 22, or in other words, regardless of thearea where wafer stages WST1, WST2 are located either within themovement area at the time of exposure or the movement area at the timeof measurement previously described, heads 60 ₁, 60 _(1a), 60 _(1b), 60₂, 60 _(2a), 60 _(2b), 60 ₃, 60 _(3a), 60 _(3b), 60 ₄, 60 _(4a) and 60_(4b) on wafer stage WST1 structure two-dimensional encoders 70 ₁, 70_(1a), 70 _(1b), 70 ₂, 70 _(2a), 70 _(2b), 70 ₃, 70 _(3a), 70 _(3b), 70₄, 70 _(4a), 70 _(4b), respectively, along with the scale plates onwhich the measurement beam (measurement light) is irradiated, and heads60 ₁, 60 _(1a), 60 _(1b), 60 ₂, 60 _(2a), 60 _(2b), 60 ₃, 60 _(3a), 60_(3b), 60 ₄, 60 _(4a) and 60 _(4b) on wafer stage WST2 structuretwo-dimensional encoders 71 ₁, 71 _(1a), 71 _(1b), 71 ₂, 71 _(2a), 71_(2b), 71 ₃, 71 _(3a), 71 _(3b), 71 ₄, 71 _(4a), 71 _(4b), respectively,along with the scale plates on which the measurement beam (measurementlight) is irradiated.

Measurement values of the two-dimensional encoders (hereinafter shortlyreferred to as an encoder as appropriate) 70 ₁, 70 _(1a), 70 _(1b), 70₂, 70 _(2a), 70 _(2b), 70 ₃, 70 _(3a), 70 _(3b), 70 ₄, 70 _(4a), 70_(4b), 71 ₁, 71 _(1a), 71 _(1b), 71 ₂, 71 _(2a), 71 _(2b), 71 ₃, 71_(3a), 71 _(3b), 71 ₄, 71 _(4a), 71 _(4b) are each supplied to maincontroller 20 (refer to FIG. 9). Of encoders 70 ₁ to 70 ₄ or encoders 71₁ to 71 ₄, main controller 20 obtains positional information of wafertables WTB1, WTB2 in directions of six degrees of freedom (X, Y, Z, θx,θy, θz) within the movement area at the time of exposure including thearea directly below projection optical system PL, based on themeasurement values of at least three encoders (that is, at least threeencoders that output effective measurement values) that face lowersurface of (sections 21 ₁ to 21 ₄ which structure) scale plate 21 onwhich two-dimensional grating RG is formed.

Main controller 20 performs calibration (to be described later on) of agrid (grid error) of a coordinate system at the time of exposure thatcorresponds to a variation of two-dimensional grating RG of scale plate21 while wafer tables WTB1, WTB2 move within the movement area at thetime of exposure including, for example, when exposure is beingperformed, using the measurement values of all of the heads in at leastthe three groups to which the heads of at least the three encodersbelong used for measuring the positional information of wafer tablesWTB1, WTB2 in directions of six degrees of freedom (X, Y, Z, θx, θy,θz).

Similarly, of encoders 70 ₁ to 70 ₄ or encoders 71 ₁ to 71 ₄, maincontroller 20 obtains positional information of wafer tables WTB1, WTB2in directions of six degrees of freedom (X, Y, Z, θx, θy, θz) within themovement area at the time of measurement including the area directlybelow alignment system ALG, based on the measurement values of at leastthree encoders (that is, at least three encoders that output effectivemeasurement values) that face the lower surface of (sections 22 ₁ to 22₄ which structure) scale plate 22 on which two-dimensional grating RG isformed.

Main controller 20 can perform calibration (to be described later on) ofa grid (grid error) of a coordinate system at the time of measurementthat corresponds to a variation of two-dimensional grating RG of scaleplate 22 while wafer tables WTB1, WTB2 move within the movement area atthe time of measurement, including, for example, when alignment is beingperformed, using the measurement values of all of the heads in at leastthe three groups to which the heads of at least the three encodersbelong used for measuring the positional information of wafer tablesWTB1, WTB2 in directions of six degrees of freedom (X, Y, Z, θx, θy,θz).

Further, in exposure apparatus 100 of the present embodiment, theposition of wafer stages WST1, WST2 (wafer tables WTB1, WTB2) can bemeasured by wafer interferometer system 18 (refer to FIG. 9),independently from encoder systems 70, 71. The measurement values ofwafer interferometer system 18 are used secondarily, for example, as abackup and the like at the time of output abnormalities of encodersystems 70, 71. Incidentally, details on wafer interferometer system 18are omitted.

Alignment system ALG, as is shown in FIG. 1, is an alignment system ofan off-axis method that is placed in a predetermined spacing on the +Xside of projection optical system PL. In the present embodiment, asalignment system ALG, as an example, an FIA (Field Image Alignment)system is used which is a type of an alignment sensor of animage-processing method that measures a mark position by illuminating amark with a broadband (wideband) light such as a halogen lamp and thelike, and performing image-processing on this mark image. Imagingsignals from alignment system ALG are supplied to main controller 20(refer to FIG. 9), via an alignment signal processing system which isnot shown.

Incidentally, alignment system ALG is not limited to the FIA system, andfor example, it is a matter of course that an alignment sensor whichperforms detection by irradiating a coherent detection light on a markand detecting scattered light or diffracted light generated from themark, or by making two diffracted lights (for example, diffracted lightof the same order or diffracted light diffracting in the same direction)generated from the mark interfere with each other can be used alone, orappropriately combined. As alignment system ALG, an alignment systemthat has a plurality of detection areas as in the one disclosed in, forexample, U.S. Patent Application Publication No. 2008/0088843 and thelike can be employed.

Other than this, in exposure apparatus 100 of the present embodiment, amulti-point focal point detection system of an oblique incidence method(hereinafter, shortly described as multi-point AF system) AF (not shownin FIG. 1, refer to FIG. 9) is provided placed at the measurementstation along with alignment system ALG and having a structure similarto the one disclosed in, for example, U.S. Pat. No. 5,448,332 and thelike. At least a part of a measurement operation by multi-point AFsystem AF is performed concurrently with the mark detection operation byalignment system ALG, and positional information of the wafer table ismeasured by the encoder system previously described during themeasurement operation. Detection signals of multi-point AF system AF issupplied to main controller 20 (refer to FIG. 9), via an AF signalprocessing system (not shown). Main controller 20 detects positionalinformation (height difference information/unevenness information) ofthe wafer W surface in the Z-axis direction, based on the detectionsignals of multi-point AF system AF and the measurement information ofthe encoder system previously described, and performs a so-calledfocus/leveling control of wafer W during scanning exposure in theexposure operation based on the information detected beforehand and themeasurement information of the encoder system previously described(positional information in the Z-axis, the θx and the θy directions).Incidentally, the multi-point AF system can be provided at the vicinityof projection unit PU within exposure station, and focus/levelingcontrol of wafer W may be performed driving the wafer table whilemeasuring the positional information (unevenness information) of thewafer surface at the time of the exposure operation.

In exposure apparatus 100, furthermore, a pair of reticle alignmentsystems 13A, 13B (not shown in FIG. 1, refer to FIG. 9) of a TTR(Through The Reticle) method which uses light of the exposure wavelengthas is disclosed in, for example, U.S. Pat. No. 5,646,413 and the like,is provided above reticle R. Detection signals of reticle alignmentsystems 13A, 13B are supplied to main controller 20, via an alignmentsignal processing system which is not shown. Incidentally, instead ofthe reticle alignment system, reticle alignment can be performed usingthe aerial image measuring instrument which is not shown provided onwafer stage WST.

FIG. 9 shows a block diagram which is partly omitted of a control systemrelated to stage control of exposure apparatus 100. This control systemis structured centering on main controller 20. Main controller 20includes a so-called microcomputer (or a workstation) consisting of aCPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (RandomAccess Memory) and the like that has overall control of the entiredevice.

In exposure apparatus 100 structured in the manner described above, whenmanufacturing a device, one of wafer stages WST1, WST2 on which thewafer is loaded is moved within the measurement station (movement areaat the time of measurement) by main controller 20, and wafer measurementoperation is performed by alignment system ALG and multi-point AFsystem. That is, to wafer W held by one of wafer stages WST1, WST2within the movement area at the time of measurement, mark detectionusing alignment system ALG, or a so-called wafer alignment (such asEnhanced Global Alignment (EGA) disclosed in, for example, U.S. Pat. No.4,780,617 and the like) and measurement of surface information (heightdifference/unevenness information) of the wafer using the multi-point AFsystem are performed. On this operation, by encoder system 70 (encoders70 ₁ to 70 ₄) or encoder system 71 (encoders 71 ₁ to 71 ₄), positionalinformation of wafer tables WTB1, WTB2 in directions of six degrees offreedom (X, Y, Z, θx, θy, θz) is obtained (measured). Incidentally,before beginning or after completing the wafer alignment, position ofthe second reference mark on the reference mark member provided on oneof wafer stages WST1, WST2 is measured by main controller 20 usingalignment system ALG. Then, array coordinates of a plurality of shotareas on wafer W calculated as results of wafer alignment are replacedwith array coordinates using the second reference mark as a reference.

After the measurement operation such as wafer alignment, one of thewafer stages (WST1 or WST2) moves to the movement area at the time ofexposure, and by main controller 20, reticle alignment and the like toobtain a positional relation between a projection center of the reticlepattern and the center of the pair of the first reference marks isperformed, using reticle alignment systems 13A, 13B, reference markmembers (not shown) on the wafer table (WTB1 or WTB2) and the like in aprocedure similar to a normal scanning stepper.

Then, by main controller 20, based on the results of the reticlealignment and the array coordinates of the plurality of shot areas usingthe second reference marks obtained as a result of the wafer alignmentas a reference, exposure operation by the step-and-scan method isperformed, and the pattern of reticle R is transferred, respectively,onto a plurality of shot areas on wafer W. The exposure operation by thestep-and-scan method is performed by alternately repeating a scanningexposure operation in which synchronous movement of reticle stage RSTand wafer stage WST1 or WST2 is performed, and a movement (stepping)operation between shots in which wafer stage WST1 or WST2 is moved to anacceleration starting position for exposure of a shot area. At the timeof the exposure operation, positional information in directions of sixdegrees of freedom (X, Y, Z, θx, θy, θz) of one of the wafer tables(WTB1 or WTB2) is obtained (measured) by encoder system 70 (encoders 70₁ to 70 ₄) or encoder system 71 (encoders 71 ₁ to 71 ₄).

Further, exposure apparatus 100 of the present embodiment is equippedwith the two wafer stages WST1, WST2. Therefore, concurrently withperforming exposure by the step-and-scan method on the wafer loaded onone of wafer stages, for example, wafer stage WST1, a concurrentprocessing operation is performed in which wafer alignment and the likeis performed on the wafer mounted on the other wafer stage WST2.

In exposure apparatus 100 of the present embodiment, as is previouslydescribed, main controller 20 obtains (measures) positional informationof wafer table WTB1 in directions of six degrees of freedom (X, Y, Z,θx, θy, θz) using encoder system 70 (refer to FIG. 9) in both themovement area at the time of exposure and the movement area at the timeof measurement. Further, main controller 20 obtains (measures)positional information of wafer table WTB2 in directions of six degreesof freedom (X, Y, Z, θx, θy, θz) using encoder system 71 (refer to FIG.9) in both the movement area at the time of exposure and the movementarea at the time of measurement.

Here, a principle and the like of position measurement in directions ofthree degrees of freedom (the X-axis direction, the Y-axis direction andthe θz direction, also shortened to (X, Y, θz))) within the XY plane byencoder systems 70, 71 will be further described. Here, measurementvalues of encoder heads 60 ₁ to 60 ₄ or encoders 70 ₁ to 70 ₄ meanmeasurement values in a measurement direction which is not in the Z-axisdirection of encoder heads 60 ₁ to 60 ₄ or encoders 70 ₁ to 70 ₄.

In the present embodiment, by employing the structure and placement ofencoder heads 60 ₁ to 60 ₄ and scale plate 21 previously described,within the movement area at the time of exposure at least three ofencoder heads 60 ₁ to 60 ₄ constantly faces (the corresponding sections21 ₁ to 21 ₄ of) scale plate 21.

FIG. 10 shows a relation between a placement of encoder heads 60 ₁ to 60₄ and each section 21 ₁ to 21 ₄ of scale plate 21 on wafer stage WST1and measurement areas A₀ to A₄ of encoder system 70. FIG. 10 shows onlyheads 60 ₁, 60 ₂, 60 ₃, and 60 ₄ which are used for measuring positionalinformation in directions of six degrees of freedom of wafer table WTB1.Incidentally, because wafer stage WST2 is structured similarly to waferstage WST1, the description here will be made only for wafer stage WST1.

In the case the center of wafer table WTB1 (coincides with the center ofthe wafer) is positioned within a first area A₁ which is within themovement area at the time of exposure that is also an area located onthe +X side and on the +Y side with respect to exposure center (thecenter of exposure area IA) P (an area within the first quadrant(however, excluding an area A₀) whose origin point is exposure centerP), heads 60 ₄, 60 ₁, 60 ₂ on wafer stage WST1 face sections 21 ₄, 21 ₁,21 ₂ of scale plate 21, respectively. In the first area A₁, effectivemeasurement values are sent to main controller 20 from heads 60 ₄, 60 ₁,60 ₂ (encoders 70 ₄, 70 ₁, 70 ₂). Incidentally, the position of waferstages WST1, WST2 in the description below means the position in thecenter of the wafer stage (coincides with the center of wafer table andthe center of the wafer, respectively). That is, instead of using theexpression, the position in the center of wafer stages WST1, WST2, theexpression used will be, the position of wafer stages WST1, WST2.

Similarly, in the case wafer stage WST1 is positioned within a secondarea A₂ which is within the movement area at the time of exposure thatis also an area located on the −X side and on the +Y side with respectto exposure center P (an area within the second quadrant (however,excluding area A₀) whose origin point is exposure center P), heads 60 ₁,60 ₂, 60 ₃ face sections 21 ₁, 21 ₂, 21 ₃ of scale plate 21,respectively. In the case wafer stage WST1 is positioned within a thirdarea A₃ which is within the movement area at the time of exposure thatis also an area located on the −X side and on the −Y side with respectto exposure center P (an area within the third quadrant (however,excluding area A₀) whose origin point is exposure center P), heads 60 ₂,60 ₃, 60 ₄ face sections 21 ₂, 21 ₃, 21 ₄ of scale plate 21,respectively. In the case wafer stage WST1 is positioned within a fourtharea A₄ which is within the movement area at the time of exposure thatis also an area located on the +X side and the −Y side with respect toexposure center P (an area within the fourth quadrant (however,excluding area A₀) whose origin point is exposure center P), heads 60 ₃,60 ₄, 60 ₁ face sections 21 ₃, 21 ₄, 21 ₁ of scale plate 21,respectively.

In the present embodiment, as is shown in FIG. 10, in the case waferstage WST1 is positioned within a cross-shaped area A₀ (an area thatpasses through exposure center P including an area of a width A-ai-2thaving a longitudinal direction in the Y-axis direction and an area of awidth B-bi-2t having a longitudinal direction in the X-axis direction(hereinafter called a zero^(th) area)), the four heads 60 ₁ to 60 ₄ onwafer stage WST1 face (the corresponding sections 21 ₁ to 21 ₄) of scaleplate 21. Accordingly, within zero^(th) area A₀, effective measurementvalues are sent from heads 60 ₄ to 60 ₄ (encoders 70 ₄ to 70 ₄) to maincontroller 20. Incidentally, in the present embodiment, adding to theabove conditions (A≥ai+2t, B≥bi+2t), conditions A≥ai+W+2t, B≥bi+L+2t canbe added, taking into consideration the size (W, L) of the shot area onthe wafer where the pattern is formed. Here, W is the width in theX-axis direction and L is the length in the Y-axis direction of the shotarea, respectively. W equals a distance of the scanning exposure sectionand L equals a stepping distance in the X-axis direction, respectively.

Main controller 20, based on the measurement values of heads 60 ₄ to 60₄ (encoders 70 ₄ to 70 ₄), calculates a position (X, Y, θz) within theXY plane of wafer stage WST1. Here, the measurement values of encoders70 ₁ to 70 ₄ (expressed as C₁ to C₄, respectively) are dependent on theposition (X, Y, θz) of wafer stage WST1, as in the following formulas(1) to (4).C ₁=−(cos θz+sin θz)X/√{square root over ( )}2+(cos θz−sin θz)Y/√{squareroot over ( )}2+√{square root over ( )}2p sin θz  (1)C ₂=−(cos θz−sin θz)X/√{square root over ( )}2−(cos θz+sin θz)Y/√{squareroot over ( )}2+√{square root over ( )}2p sin θz  (2)C ₃=(cos θz+sin θz)X/√{square root over ( )}2−(cos θz−sin θz)Y/√{squareroot over ( )}2+√{square root over ( )}2p sin θz  (3)C ₄=(cos θz−sin θz)X/√{square root over ( )}2+(cos θz+sin θz)Y/√{squareroot over ( )}2+√{square root over ( )}2p sin θz  (4)

However, p, as is shown in FIG. 6, is the distance in the X-axis and theY-axis direction of each of the heads 60 ₁ to 60 ₄ from the center ofwafer table WTB1 (WTB2).

Main controller 20 calculates the position (X, Y, θz) within the XYplane of wafer stage WST1 by specifying three heads (encoders) that facescale plate 21 corresponding to areas A₀ to A₄ in which wafer stage WST1is positioned, forming simultaneous equations by choosing formulas thatthe measurement values of these heads follow from formulas (1) to (4)above, and solving the simultaneous equations using the measurementvalues of the three heads (encoders). For example, in the case waferstage WST1 is positioned within the first area A₁, main controller 20forms simultaneous equations from formulas (1), (2) and (4) that themeasurement values of heads 60 ₁, 60 ₂, 60 ₄ (encoders 70 ₁, 70 ₂, 70 ₄)follow, and solves the simultaneous equations by substituting themeasurement values of each head into the left side of formulas (1), (2),and (4), respectively.

Incidentally, in the case wafer stage WST1 is positioned withinzero^(th) area A₀, main controller 20 can select three arbitrary headsfrom heads 60 ₁ to 60 ₄ (encoder 70 ₁ to 70 ₄). For example, after waferstage WST1 has moved to the zero^(th) area from the first area, heads 60₁, 60 ₂, 60 ₄ (encoders 70 ₁, 70 ₂, 70 ₄) corresponding to the firstarea should be selected.

Main controller 20 drives (performs position control of) wafer stageWST1 within the movement area at the time of exposure, based on resultsof the calculation (X, Y, θz) described above.

In the case wafer stage WST1 is positioned within the movement area atthe time of measurement, main controller 20 measures positionalinformation in directions of three degrees of freedom (X, Y, θz), usingencoder system 70 (encoders 70 ₁ to 70 ₄). Here, the measurementprinciple and the like are the same as the case previously describedwhen wafer stage WST1 is positioned within the movement area at the timeof exposure, except for the point that exposure center P is replacedwith the detection center of alignment system ALG and (sections 21 ₁ to21 ₄ of) scale plate 21 is replaced with (sections 22 ₁ to 22 ₄ of)scale plate 22.

Furthermore, main controller 20 uses three heads of heads 60 ₁ to 60 ₄facing scale plates 21, 22 while switching to three heads with at leastone different, according to the position of wafer stages WST1, WST2.Here, on switching the encoder heads, a joint processing is performed toassure continuity of the measurement values of the position of the waferstage, as is disclosed in, for example, U.S. Patent ApplicationPublication No. 2008/0094592 and the like. Further, in the presentembodiment, in a method similar to the method disclosed in, for example,U.S. Patent Application Publication No. 2011/0053061, switching betweenheads 60 ₁ to 60 ₄ at the time of exposure operation by thestep-and-scan method and joint processing are performed.

Next, the principle and the like for position measurement in directionsof three degrees of freedom (Z, θx, θy) by encoder systems 70, 71 willbe described furthermore. Here, measurement values of encoder heads 60 ₁to 60 ₄ or encoders 70 ₁ to 70 ₄ mean measurement values in the Z-axisdirection of encoder heads 60 ₁ to 60 ₄ or encoders 70 ₁ to 70 ₄.

In the present embodiment, by employing the structure and the placementof encoder heads 60 ₁ to 60 ₄ and scale plate 21 previously described,within the movement area at the time of exposure, at least three ofencoder heads 60 ₁ to 60 ₄ face (the corresponding sections 21 ₁ to 21 ₄of) scale plate 21, corresponding to areas A₀ to A₄ in which wafer stageWST1 (WST2) is positioned. Effective measurement values from the heads(encoders) facing scale plate 21 is sent to main controller 20.

Main controller 20 calculates a position (Z, θx, θy) of wafer stagesWST1 (WST2), based on the measurement values of encoders 70 ₁ to 70 ₄.Here, measurement values in the Z-axis direction (expressed as D₁ to D₄,respectively, to distinguish them from measurement values C₁ to C₄ inthe measurement direction which is not the Z-axis direction previouslydescribed, that is, an uniaxial direction within the XY plane) ofencoders 70 ₁ to 70 ₄ are dependent on the position (Z, θx, θy) of waferstage WST1 (WST2), as in the following formulas (5) to (8).D ₁ =−p tan θy+p tan θx+Z  (5)D ₂ =p tan θy+p tan θx+Z  (6)D ₃ =p tan θy−p tan θx+Z  (7)D ₄ =−p tan θy−p tan θx+Z  (8)

However, p is a distance (refer to FIG. 6) of heads 60 ₁ to 60 ₄ in theX-axis and the Y-axis direction, from the center of wafer table WTB1(WTB2).

Main controller 20 calculates the position (Z, θx, θy) of wafer stageWST1 (WST2) by choosing formulas that the measurement values of threeheads (encoders) follow from formulas (5) to (8) corresponding to areasA₀ to A₄ in which wafer stage WST1 (WST2) is positioned, and bysubstituting the measurement values of the three heads (encoders) intosimultaneous equations structured from the three chosen formulas andsolving the simultaneous equations. For example, in the case wafer stageWST1 (or WST2) is positioned within the first area A₁, main controller20 forms simultaneous equations from formulas (5), (6), and (8) that themeasurement values of heads 60 ₁, 60 ₂, 60 ₄ (encoders 70 ₁, 70 ₂, 70 ₄)(or heads 60 ₁, 60 ₂, 60 ₄ (encoders 71 ₁, 71 ₂, 71 ₄) follow, andsolves the equations by substituting the measurement values into theleft side of formulas (5), (6), and (8), respectively.

Incidentally, in the case wafer stage WST1 (or WST2) is positionedwithin zero^(th) area A₀, three arbitrary heads can be selected fromheads 60 ₁ to 60 ₄ (encoders 70 ₁ to 70 ₄) (or heads 60 ₁ to 60 ₄(encoders 71 ₁ to 71 ₄)), and the simultaneous equations formed from theequations that the measurement values of the chosen three heads followcan be used.

Main controller 20 performs focus/leveling control on wafer stage WST1(or WST2) within the movement area at the time of exposure, based on thecalculation results (Z, θx, θy) above and the height differenceinformation (focus mapping data) previously described.

In the case wafer stage WST1 (or WST2) is positioned within the movementarea at the time of measurement, main controller 20 measures positionalinformation in directions of three degrees of freedom (Z, θx, θy), usingencoder system 70 or 71. Here, the measurement principle and the like issimilar to the case when wafer stage WST1 is positioned within themovement area at the time of exposure, except for the point that theexposure center is replaced with the detection center of alignmentsystem ALG and that (sections 21 ₁ to 21 ₄ of) scale plate 21 isreplaced with (sections 22 ₁ to 22 ₄ of) scale plate 22. Main controller20 performs focus/leveling control on wafer stage WST1 or WST2, based onmeasurement values of encoder system 70 or 71. Incidentally, in themovement area at the time of measurement (measurement station),focus/leveling does not necessarily have to be performed. That is,acquisition of mark position and height difference information (focusmapping data) should be performed, and by subtracting the Z tilt at thetime of acquisition (at the time of measurement) of the wafer stageheight difference information from the height difference information,height difference information of a reference surface of the wafer stage,such as for example, the upper surface serving as a reference, should beobtained. Then, at the time of exposure, focus/leveling becomespossible, based on this height difference information and positionalinformation in directions of three degrees of freedom (Z, θx, θy) (ofthe reference surface) of the wafer stage.

Furthermore, main controller 20 uses three heads of heads 60 ₁ to 60 ₄facing scale plates 21, 22 while switching to three heads with at leastone different, according to the position of wafer stages WST1, WST2.Here, on switching the encoder heads, the joint processing as ispreviously described is performed to secure continuity of themeasurement values of the position of wafer stage WST1 (or WST2).

Next, correction (calibration) of grid variation quantity of thecoordinate system at the time of exposure in exposure apparatus 100related to the present embodiment is described, which is performed whilethe series of sequences described above is performed. Here, the casewill be described when wafer stage WST1 moves in the movement area atthe time of exposure.

This correction (calibration) of the grid variation quantity isperformed by main controller 20, concurrently with the position controlof wafer table WTB1 in directions of six degrees of freedom which isperformed based on the measurement values of the three encoders chosenfrom encoders 70 ₁ to 70 ₄ as is previously described.

Main controller 20, for example, takes in the measurement values in an adirection of heads 60 ₁, 60 _(1a), (encoders 70 ₁, 70 _(1a)) andsequentially integrates difference data which is expressed in formula(9) below, that is, deviation Δα/δx corresponding to the X position ofthe grid in the α direction (α grid), each time wafer stage WST1 movesby Δx in the X-axis direction in a state, for example, where heads 60 ₁,60 _(1a), 60 _(1b) belonging to the first head group 61 ₁ are facing thecorresponding section 21 ₁ of scale plate 21, for example, duringexposure and the like. This allows a discrete distribution of the α gridvariation quantity in the X-axis direction to be obtained.Δα/δx=ζ ₁(x−Δx,y)−ζ₁(x,y)  (9)

Further, main controller 20, for example, takes in the measurementvalues in the a direction of heads 60 ₁, 60 _(1b), (encoders 70 ₁, 70_(1b)) and sequentially integrates difference data which is expressed informula (10) below, that is, deviation Δα/δy corresponding to the Yposition of the α grid, each time wafer table WTB1 moves by Δy in theY-axis direction in a state, for example, where heads 60 ₁, 60 _(1a), 60_(1b) belonging to the first head group 61 ₁ are facing thecorresponding section 21 ₁ of scale plate 21, for example, duringexposure and the like. This allows a discrete distribution of the α gridvariation quantity in the Y-axis direction to be obtained.Δα/δy=ζ ₁(x,−y−Δy)−ζ₁(x,y)  (10)

Main controller 20 can obtain an a correction map for correcting a drift(α grid variation) generated in the first quadrant section (the firstsection 21 ₁ of scale plate 21) of two-dimensional grating RG expressedas a function ζ₁ (x, y), from the discrete distribution of the α gridvariation quantity in the X-axis direction described above and thediscrete distribution of the α grid variation quantity in the Y-axisdirection.

Main controller 20 takes in measurement values in the a direction, forexample, of heads 60 ₃, 60 _(3a) (encoders 70 ₃, 70 _(3a)) andsequentially integrates difference data similar to formula (9), eachtime wafer stage WST1 moves by Δx in the X-axis direction in a state,for example, where heads 60 ₃, 60 _(3a), 60 _(3b) belonging to the thirdhead group 61 ₃ face the corresponding section 21 ₃ of scale plate 21,for example, during exposure and the like, along with taking inmeasurement values in the α direction, for example, of heads 60 ₃, 60_(3b) (70₃, 70 _(3b)) and sequentially integrates difference datasimilar to formula (10), each time wafer stage WST1 moves by Δy in theY-axis direction. Then, main controller 20 obtains the a correction mapfor correcting the drift (α grid variation) generated in the thirdquadrant section (the third section 21 ₃ of scale plate 21) oftwo-dimensional grating RG expressed as a function (ζ₃ (x, y)), from thediscrete distribution of the α grid variation quantity in the X-axisdirection and the discrete distribution of the α grid variation quantityin the Y-axis direction that are obtained from the integration of thedifference data described above.

Main controller 20 takes in measurement values in a β direction, forexample, of heads 60 ₂, 60 _(2a) (encoders 70 ₂, 70 _(2a)) andsequentially integrates difference data expressed in formula (11) below,each time wafer stage WST1 moves by Δx in the X-axis direction in astate, for example, where heads 60 ₂, 60 _(2a), 60 _(2b) belonging tothe second head group 61 ₂ are facing the corresponding section 21 ₂ ofscale plate 21, for example, during exposure and the like, along withtaking in measurement values in the β direction, for example, of heads60 ₂, 60 _(2b) (70 ₂, 70 _(2b)) and sequentially integrates differencedata expressed in formula (12) below, each time wafer stage WST1 movesby Δy in the Y-axis direction. Then, main controller 20 obtains a βcorrection map for correcting a drift (β grid variation) generated inthe second quadrant section (the second section 21 ₂ of scale plate 21)of two-dimensional grating RG expressed as a function ζ₂ (x, y), fromthe discrete distribution of the β grid variation quantity in the X-axisdirection and the discrete distribution of the β grid variation quantityin the Y-axis direction that are obtained from the integration of thedifference data described above.Δβ/δx=ζ ₂(x−Δx,y)−ζ₂(x,y)  (11)Δβ/δy=ζ ₂(x,y−Δy)−ζ₂(x,y)  (12)

Main controller 20 takes in measurement values in the β direction, forexample, of heads 60 ₄, 60 _(4a) (encoders 70 ₄, 70 _(4a)) andsequentially integrates difference data similar to formula (11), eachtime wafer stage WST1 moves by Δx in the X-axis direction in a state,for example, where heads 60 ₄, 60 _(4a), 60 _(4b) belonging to thefourth head group 61 ₄ are facing the corresponding section 21 ₄ ofscale plate 21, for example, during exposure and the like, along withtaking in measurement values in the β direction, for example, of heads60 ₄, 60 _(4b) (70 ₄, 70 _(4b)) and sequentially integrates differencedata similar to formula (12), each time wafer stage WST1 moves by Δy inthe Y-axis direction. Then, main controller 20 obtains the β correctionmap for correcting a drift (β grid variation) generated in the fourthquadrant section (the fourth section 21 ₄ of scale plate 21) oftwo-dimensional grating RG expressed as a function (ζ₄ (x, y)), from thediscrete distribution of the β grid variation quantity in the X-axisdirection and the discrete distribution of the β grid variation quantityin the Y-axis direction that are obtained from the integration of thedifference data described above.

Main controller 20 also makes a Z correction map in a similar manner asthe α correction map and the β correction map described above, forexample, during exposure and the like.

That is, main controller 20, takes in measurement values in the Z-axisdirection, for example, of heads 60 ₁, 60 _(1a) (encoders 70 ₁, 70_(1a)) and sequentially integrates the difference data expressed informula (13) below, each time wafer stage WST1 moves by Δx in the X-axisdirection in a state, for example, where heads 60 ₁, 60 _(1a), 60 _(1b)belonging to the first head group 61 ₁ are facing the correspondingsection 21 ₁, for example, during exposure and the like, along withtaking in measurement values in the Z-axis direction, for example, ofheads 60 ₁, 60 _(1b) (70 ₁, 70 _(1b)) and sequentially integratesdifference data expressed in formula (14) below, each time wafer stageWST1 moves by Δy in the Y-axis direction. Then, main controller 20obtains the Z correction map for correcting a Z grid variation (drift)generated in the first quadrant section (the first section 21 ₁ of scaleplate 21) of two-dimensional grating RG expressed as a function 11 ₁ (x,y), from the discrete distribution of the Z grid variation quantity inthe X-axis direction and the discrete distribution of the Z gridvariation quantity in the Y-axis direction that are obtained from theintegration of the difference data described above.ΔZ/δx=η ₁(x−Δx,y)−η₁(x,y)  (13)ΔZ/δy=η ₁(x,y−Δy)−η₁(x,y)  (14)

Main controller 20 takes in and performs integration of the differencedata in a manner similar to the description above, each time wafer stageWST1 moves by Δx and moves by Δy, also for heads belonging to the secondhead group, the third head group and the fourth head group in a statefacing scale plate 21, for example, during exposure and the like, andobtains the Z correction map, along with reproducing functions (η₂ (x,y), η₃ (x, y), η₄ (x, y), respectively) that express the drift shape (Zgrid variation).

Main controller 20 repeatedly performs the difference measurementdescribed above, concurrently with the position measurement indirections of six degrees of freedom of wafer table WTB described above,and performs an update of grid errors of the coordinate system ofencoder system 70. Hereinafter, this update of grid errors will also becalled refreshing of the coordinate system of encoder system 70.

As is previously described, main controller 20 uses three of heads 60 ₁to 60 ₄ facing scale plate 21, switching to three with at least onedifferent according to the position of wafer stage WST1, for example, atthe time of exposure. That is, main controller 20 drives wafer tableWTB1 based on the positional information of wafer table WTB1 obtained bythree of heads 60 ₁ to 60 ₄ (three of encoders 70 ₁ to 70 ₄), along withswitching at least one of the three heads used for calculating thepositional information of wafer table WTB1 according to the position ofwafer table WTB1 to a head belonging to another head group which is notused for calculating the positional information of wafer table WTB1.Main controller 20, with this switching, switches the head group subjectto taking in the difference data for calibration of the grid errors oftwo-dimensional grating RG of scale plate 21 described above to anotherhead group. In the present embodiment, simultaneously with the switchingof the head used for position measurement of wafer table WTB, switchingof redundant heads used for difference measurement previously describedis performed.

Main controller 20 performs refreshing of the coordinate system ofencoder system 71 similarly to the description above in the case waferstage WST2 is moving in the movement area at the time of exposure,including the time of exposure.

Now, during exposure, because movement of wafer stages WST1, WST2 isperformed according to a shot map and wafer stages WST1, WST2 pass onlylimited areas, difference data that can be acquired is little.

Therefore, main controller 20, on the refreshing of the coordinatesystems of encoder systems 70, 71 described above, corrects in areal-time manner a primary component which is a low-order component ofgrid variation from the integration of difference data, such as, forexample, only scaling (α, β grids), and bending (Z grid), as ispreviously described.

Then, the integration value of the difference data is monitored, and inthe case variation quantity (correction quantity) of the low-ordercomponent (primary component) becomes larger than a first quantitydefined beforehand, a more elaborate correction is to be performed.Here, a more elaborate correction means, for example, to performacquisition of difference data previously described by moving waferstages WST1, WST2 in almost the entire area of their effective strokesto acquire more difference data, and based on the more acquireddifference data, to perform grid variation quantity (error) correctionsimilar to the one previously described, or variation quantitycorrection of α, β and Z grids subject to at least a secondary componentwhich is performed in a method similar to the following description in awider range of two-dimensional grating RG of scale plate 21.

In the case variation quantity (correction quantity) of the low-ordercomponent (primary component) is larger than a second amount definedbeforehand which is larger than the first quantity, main controller 20gives notice to an operator, for example, by display and the like,informing that correction subject to components of a higher order isrequired. In response to this notice, in the case correction of a higherorder is instructed from the operator, main controller 20 loads areference wafer (a resist is coated on its surface) having a pluralityof reference marks arranged as is designed formed on wafer table WTB1 orWTB2, and loads a measurement reticle having a plurality of marks placedin a predetermined positional relation on reticle stage RST. Then,exposure is performed, for example, in a step-and-repeat method (or astep-and-scan method). After the exposure has been completed, maincontroller 20 carries the reference wafer after exposure, for example,to a coater/developer which is in-line connected to exposure apparatus100, and with this gives instructions for development. Then, whenreceiving notice that development of the reference wafer has beencompleted from the coater/developer, main controller 20 loads thereference wafer after development again on wafer table WTB1 or WTB2, andsequentially detects a position with respect to the reference markcorresponding to the mark consisting of the resist image formed on thereference wafer, for example, with alignment system ALG. Then, based onthe detection results, correction of the variation quantity of α, β andZ grids subject to higher-order components is performed.

Other than this, a setting can be employed, in which, for example, theoperator sets a threshold value (for example, a third amount definedbeforehand which is larger than the second quantity) for the variationquantity (correction quantity) of the low-order component (primarycomponent) previously described, and main controller 20 monitors whetherthe variation quantity of the low-order component exceeds the thresholdvalue or not, and in the case the variation quantity (correctionquantity) exceeds the threshold value, a notice is to be sent to theoperator informing that grid maintenance is required. That is, thevariation quantity (correction quantity) of the low-order componentpreviously described can be used as a monitor index to judge whether ornot grid maintenance is required.

As is described in detail so far, according to exposure apparatus 100related to the present embodiment, for example, when wafer stage WST1(or WST2) is located in the movement area at the time of exposure suchas during exposure, wafer table WTB1 or WTB2 (wafer stage WST1 or WST2)is driven by main controller 20, based on positional information indirections of six degrees of freedom obtained using three of encoders 70₁ to 70 ₄ of encoder system 70 (or three of encoders 71 ₁ to 71 ₄ ofencoder system 71). And concurrently with this driving of wafer tableWTB1 or WTB2 (wafer stage WST1 or WST2), by main controller 20, in thehead group facing scale plate 21 of the first head group 61 ₁, thesecond head group 61 ₂, the third head group 61 ₃ and the fourth headgroup 61 ₄, difference data of measurement values in measurementdirections (α direction and Z direction, or β direction and Z direction)of one head 60 _(i) serving as a reference belonging to each group andtwo heads 60 _(ia) and 60 _(ib) (i=1 to 4), respectively, are taken in,and based on the difference data which are taken in, it becomes possibleto monitor variation quantity of grids in measurement directions (αdirection and Z direction, or β direction and Z direction) for sectionscorresponding to four sections 21 ₁ to 21 ₄ of two-dimensional gratingRG formed on the lower surface of scale plate 21, respectively. Further,by main controller 20, calibration (correction) of the grid errors(especially the low-order component), that is, refreshing of thecoordinate systems of encoder systems 70, 71 is performed in a real-timemanner. Therefore, according to exposure apparatus 100, by encodersystem 70 or 71 with two-dimensional grating RG formed on the lowersurface of scale plate 21 serving as a measurement surface, position indirection of six degrees of freedom within the movement area at the timeof exposure of wafer stage WST1 or WST2 can be measured and controlledwith good accuracy for over a long period, which in turn allows thepattern of reticle R to be transferred with good accuracy on theplurality of shot areas on wafer W.

In exposure apparatus 100 related to the present embodiment, by maincontroller 20, refreshing of the coordinate systems of encoder systems70, 71 is executed in a real-time manner on exposure and the like.

Therefore, even if in the case scale plate 21 (two-dimensional gratingRG) increases furthermore in size along with wafer stages WST1, WST2 tocope with 450 mm wafers, it becomes possible to measure the position indirections of six degrees of freedom within the movement area at thetime of exposure of wafer table WTB1 or WTB2 with good accuracy for overa long period.

Further, in exposure apparatus 100, main controller 20 can executerefreshing of the coordinate systems of encoder systems 70, 71 in areal-time manner, while wafer stage WST1 or WST2 is moving within themovement area at the time of measurement such as during wafer alignmentmeasurement (mark detection by alignment system ALG) and at the time ofdetection of positional information in the Z-axis direction (heightdifference information/unevenness information) of the wafer W surfacewhich is performed concurrently with the wafer alignment. In such acase, accuracy of wafer alignment such as EGA and focus/leveling controlaccuracy of wafer W during scanning exposure can be maintained at highprecision for over a long period.

Furthermore, in exposure apparatus 100 related to the presentembodiment, placement spacing A, B of heads 60 ₁ to 60 ₄ are eachdecided to be larger than the sum of widths ai, bi of the openings ofscale plates 21, 22 and sizes W, L of the shot areas, respectively. Thisallows positional information of wafer stages WST1, WST2 to be measuredwithout switching heads 60 ₁ to 60 ₄ during scanning (constant velocity)drive of wafer stages WST1, WST2 that hold the wafer for exposure of thewafer. Accordingly, the pattern can be formed on the wafer with goodprecision, and overlay accuracy can be maintained with high precision,especially from exposure of a second layer (second layer) onward.

Incidentally, in the description of the embodiment above, while the fourheads 60 ₁, 60 ₂, 60 ₃, 60 ₄ for position measurement of the wafer tableprovided at the four corners of the wafer table upper surface satisfythe placement conditions described above, as is obvious from theplacement of heads 60 _(ia), 60 _(ib) and 60 _(i) belonging to each headgroup 61 _(i) (i=1 to 4) (refer to FIG. 2), heads 60 _(1a), 60 _(2a), 60_(3a), 60 _(4a), and heads 60 _(1b), 60 _(2b), 60 _(3b), 60 _(4b) alsosatisfy placement conditions similar to the conditions described above.

Incidentally, in the embodiment above, while the case has been describedwhere scale plates 21, 22 are each structured from four sections andfour head groups 61 ₁ to 61 ₄ corresponding to this are provided onwafer stages WST1, WST2, the present invention is not limited to this,and scale plates 21, 22 can be structured from a single member. In thiscase, two-dimensional grating RG can be a single two-dimensional gratinghaving a large area. In such a case, when movement strokes of waferstages WST1, WST2 are sufficiently large, in addition to two heads (forexample, two of heads 60 ₂ to 60 ₄) that allow position measurement ofwafer stages WST1, WST2 in a predetermined degrees of freedom, such asfor example, six degrees of freedom along with head 60 ₁, only tworedundant heads 60 _(1a), 60 _(1b) belonging to the first head group 61₁ can be provided.

Further, the placement of the heads belonging to each head group in thedescription of the embodiment above is a mere example. For example, as aplacement of the heads belonging to the first head group, a placementcan be employed as is shown in, for example, FIG. 11A. In this case, onrefreshing of the coordinate system, refreshing of the coordinate systemcan be performed in a similar manner as in the embodiment above bysupposing that the function expressing the drift shape (variation of α,β, Z grids) previously described is not function x, y, but is functionα, β.

Or, as a placement of the heads belonging to the first head group 61 ₁,for example, a placement can be employed as is shown in FIG. 11B. Inthis case, measurement directions of heads 60 ₁, 60 _(1a), 60 _(1b) arein 2 directions, which are the X-axis direction and the Z-axisdirection. Accordingly, in the first section of scale plate 21 where theheads belonging to the first head group 61 ₁ faces, a one-dimensional ora two-dimensional grating is provided having a periodic direction atleast in the X-axis direction. In the case the placement shown in FIG.11A or FIG. 11B is employed as the placement of the heads belonging tothe first head group, as the placement for the heads belonging to eachof the second head group, the third head group, and the fourth headgroup, a placement point-symmetric to the placement shown in FIG. 11A orFIG. 11B with respect to the wafer table center or line-symmetric to theplacement shown in FIG. 11A or FIG. 11B with respect to a straight lineparallel to the X-axis or the Y-axis that passes through the center(however, the measurement direction within the XY plane of a headbelonging to at least one group of the second head group, the third headgroup, and the fourth head group is orthogonal to the measurementdirection of the head belonging to the first head group) is employed.

Incidentally, while the case has been described where three heads belongto each head group, the embodiment is not limited to this, and each headgroup may have two heads. For example, in the case at least onedirection of the X-axis direction and the Y-axis direction is includedin the measurement direction of the two heads, these two heads arepreferably placed apart in directions intersecting the X-axis and theY-axis, for example, similarly to heads 60 _(1a), 60 _(1b) in FIG. 11B.Further, in the case at least one direction of the a direction and the βdirection previously described is included in the measurement directionof the two heads, these two heads are preferably placed apart in theX-axis direction (or the Y-axis direction) intersecting the α directionand the β direction, for example, similarly to heads 60 _(1a), 60 _(1b)in FIG. 11A.

Or, four or more heads may belong to each head group. Also in this case,a placement of the heads is employed in which all heads belonging toeach head group are not positioned on the same straight line. In thiscase, on the refreshing of the coordinate system at the time of exposurepreviously described, difference data of measurement values in a commonmeasurement direction of the head serving as a reference and of each ofthe remaining heads belonging to each head group that are used formeasurement of positional information in directions of six degrees offreedom of the wafer table can be acquired, or difference data in thecommon measurement direction of all heads different from one anotherbelonging to each head group can be acquired. The point is, anyplacement can be employed as long as difference data in the commonmeasurement direction of the heads different from one another belongingto each head group, including the difference data of the measurementvalues in the common measurement direction of the head serving as areference and of at least two heads of each of the remaining headsbelonging to each head group that are used for the measurement ofpositional information belonging to each head group are acquired, andbased on the difference data which has been acquired, variation quantityof the grid in the common measurement direction of scale plate 21(two-dimensional grating RG) is monitored and the grid error can becalibrated.

In the case four or more heads belong to each head group, at the time ofrefreshing of the coordinate system, because more difference data can beacquired in the X-axis or the Y-axis direction at one time, calibrationof grid variation quantity (grid error) targeting on components of apredetermined order which is a second order or more can be performedreal time. And, in this case, as a mode of “a more detailed grid errorcorrection” previously described, calibration of grid variation quantity(grid error) targeting on components of a higher order than thepredetermined order can be performed similarly to the previousdescription, for example, using a reference wafer and the like.

Incidentally, in the embodiment described above, while the case has beendescribed where only the measurement value of one head serving as areference of the three heads belonging to each head group is used forcalculating the position of wafer tables WTB1, WTB2 in directions of sixdegrees of freedom, the embodiment is not limited to this, andmeasurement values of at least two of the three heads belonging to eachhead group can be used to calculate the position of wafer tables WTB1,WTB2 in directions of six degrees of freedom. For example, an average ofthe measurement values of the three heads belonging to each head groupcan be used to calculate the position of wafer tables WTB1, WTB2 indirections of six degrees of freedom. In such a case, by an averagingeffect, position measurement of a higher accuracy becomes possible.

Further, in the embodiment above, while the case has been describedwhere a two-dimensional head having a measurement direction in twodirections which are one direction within the XY plane and the Z-axisdirection was used as each head, and grid error calibration (correction)of the coordinate system at the time of exposure is performed in the twodirections, the embodiment is not limited to this. For example, the griderror calibration (correction) of the coordinate system at the time ofexposure can be performed in one direction of the one direction withinthe XY plane and the Z-axis direction. Further, as each head, athree-dimensional head having measurement directions in two directionsorthogonal within the XY plane and the Z-axis direction can be used. Or,for example, as heads 60 _(ia), 60 _(ib), a one-dimensional head or atwo-dimensional head 60 _(i) head 60 _(i) consisting of atwo-dimensional head or a three-dimensional head that has at least onecommon measurement direction of the two or three measurement directionsof head 60 _(i), can be used. In the case of using a one-dimensionalhead whose measurement direction is in an uniaxial direction within theXY plane, combined with this, a surface position sensor of a non-encodermethod whose measurement direction is in the Z-axis direction can beemployed.

Incidentally, in the embodiment described above, while the example wasdescribed where two-dimensional gratings RG were formed scale on thelower surfaces of sections 21 ₁ to 21 ₄, 22 ₁ to 22 ₄ of plates 21, 22,respectively, the embodiment is not limited to this, and the embodimentdescribed above can also be applied in the case a one-dimensionalgrating is formed whose periodic direction is only the measurementdirection of the corresponding encoder heads 60 ₁ to 60 ₄ (the uniaxialdirection within the XY plane).

Further, in the embodiment described above, while the exposure apparatuswas described equipped with an encoder system having heads mounted onwafer stages WST1, WST2 and scale plates 21, 22 (two-dimensionalgratings RG) placed external to wafer stages WST1, WST2, the embodimentis not limited to this, and can also be applied to an exposure apparatusequipped with a type of encoder system that has a plurality of headsprovided external to the wafer stage, such as for example, above (orbelow), and a measurement surface such as a grating and the likeprovided facing this, on the upper surface (or lower surface) of thewafer stage, such as the exposure apparatus and the like disclosed in,for example, U.S. Patent Application Publication No. 2008/0088843 andthe like.

Incidentally, in the embodiment described above, while the case has beendescribed where the exposure apparatus was a scanning stepper, theembodiment is not limited to this, and the embodiment described abovecan also be applied to a stationary type exposure apparatus such as astepper. In the case of a stepper and the like, by measuring theposition of the stage on which an object subject to exposure is mountedwith the encoder, generation of position measurement error caused by airfluctuation can be suppressed to almost zero different from the casewhen measuring the position of the stage by an interferometer, and basedon measurement values of the encoder, positioning of the stage can beperformed with high precision, and transfer of the reticle pattern ontothe wafer can consequently be performed with high precision. Further,the embodiment above can also be applied to a projection exposureapparatus by a step-and-stitch method in which a shot area and a shotarea are synthesized.

Further, in the embodiment described above, while the example was givenin the case exposure apparatus 100 is a twin stage type exposureapparatus equipped with two wafer stages, the embodiment is not limitedto this, and as is disclosed in, for example, U.S. Patent ApplicationPublication No. 2007/0211235 and U.S. Patent Application Publication No.2007/0127006 and the like, the embodiment described above can also beapplied to an exposure apparatus which is equipped with a measurementstage including a measurement member (such as, for example, a referencemark, and/or a sensor) separate from the wafer stage, or a single stageexposure apparatus which is equipped with one wafer stage.

Further, the exposure apparatus in the embodiment described above can bea liquid immersion type as is disclosed in, for example, PCTInternational Publication No. 99/49504, U.S. Patent ApplicationPublication No. 2005/0259234 and the like.

Further, the projection optical system in the exposure apparatus in theembodiment described above is not limited only to a reduction system,and can either be an equal magnifying or a magnifying system, andprojection optical system PL is not limited only to a refractive system,and can either be a reflection system or a catadioptric system, and theprojection image can either be an inverted image or an erected image.

Further, illumination light IL is not limited to an ArF excimer laserbeam (wavelength 193 nm), and can be ultraviolet light such as a KrFexcimer laser beam (wavelength 248 nm), or a vacuum-ultraviolet lightsuch as an F2 excimer laser beam (wavelength 157 nm). As is disclosedin, for example, U.S. Pat. No. 7,023,610, as the vacuum-ultravioletlight, a harmonic wave can be used which is obtained by amplifying asingle wavelength laser beam in an infrared or visible range oscillatedfrom a DFB semiconductor laser or a fiber laser, with a fiber amplifierdoped with, for example, erbium (or both erbium and ytterbium) andperforming wavelength conversion into an ultraviolet light using anon-linear optical crystal.

Further, in the embodiment described above, while a transmissive mask(reticle) on which a predetermined light shielding pattern (or a phasepattern or a light attenuation pattern) was formed on the transmissivesubstrate, was used, instead of this reticle, as is disclosed in, forexample, U.S. Pat. No. 6,778,257, an electron mask (also called avariable shaped mask, an active mask, or an image generator, andincludes, for example, a DMD (Digital Micro-mirror Device) which is akind of a non-emission type image display device (spatial lightmodulator) and the like) which forms a light-transmitting pattern, areflection pattern, or an emission pattern, based on electronic data ofthe pattern to be exposed can also be used. In the case of using such avariable shaped mask, because the stage on which the wafer or the glassplate and the like is mounted is scanned with respect to the variableshaped mask, by measuring the position of the stage by using theencoder, an effect equivalent to the embodiment described above can beobtained.

Further, the embodiment described above can also be applied to anexposure apparatus (lithography system) that forms a line-and-spacepattern on wafer W by forming an interference fringe on wafer W, as isdisclosed in PCT International Publication No. 2001/035168.

Furthermore, the embodiment described above can also be applied to anexposure apparatus which synthesizes two reticle patterns on a wafer viathe projection optical system and performs double exposure almostsimultaneously on a shot area on the wafer by performing scanningexposure once, as is disclosed in, for example, U.S. Pat. No. 6,611,316.

Further, the object on which the pattern should be formed (the objectsubject to exposure on which the energy beam is irradiated) in theembodiment above is not limited to the wafer, and may be other objectssuch as a glass plate, a ceramic substrate, a film member, or a maskblank.

Furthermore, the usage of the exposure apparatus is not limited to theexposure apparatus for manufacturing semiconductors and can be widelyapplied, for example, to an exposure apparatus for liquid crystals thattransfers a liquid crystal display devices pattern onto a square-shapedglass plate, an exposure apparatus for manufacturing organic ELs, thinfilm magnetic head, an imaging element (such as a CCD), a micromachineand a DNA chip and the like. Further, the embodiment described above canalso be applied to an exposure apparatus that transfers a circuitpattern onto a glass substrate or a silicon wafer for manufacturing notonly microdevices such as semiconductor devices but also a reticle or amask that is used in an optical exposure apparatus, and EUV exposureapparatus, an X-ray exposure apparatus, an electron beam exposureapparatus and the like.

Electronic devices such as semiconductor devices are manufacturedthrough steps such as; a step for performing function/performance designof a device, a step for making a reticle based on the design step, astep for making a wafer from a silicon material, a lithography step fortransferring a pattern of a mask (reticle) onto the wafer by theexposure apparatus (pattern formation apparatus) and the exposure methodrelated to the embodiment previously described, a development step fordeveloping the wafer which has been exposed, an etching step forremoving by the etching an exposed member of an area other than the areawhere the resist remains, a resist removing step for removing the resistthat is no longer necessary since etching has been completed, a deviceassembly step (including a dicing process, a bonding process, and apackage process), and an inspection step. In this case, in thelithography step, because the device pattern is formed on the waferusing the exposure apparatus of the embodiment described above in theexposure method previously described, a highly integrated device can bemanufactured with good productivity.

Further, the exposure apparatus (pattern formation apparatus) of theembodiment described above is manufactured by assembling various kindsof subsystems that include the respective constituents which are recitedin the claims of the present application so as to keep predeterminedmechanical accuracy, electrical accuracy and optical accuracy. In orderto secure these various kinds of accuracy, before and after theassembly, adjustment to achieve the optical accuracy for various opticalsystems, adjustment to achieve the mechanical accuracy for variousmechanical systems, and adjustment to achieve the electrical accuracyfor various electric systems are performed. A process of assemblingvarious subsystems into the exposure apparatus includes mechanicalconnection, wiring connection of electric circuits, piping connection ofpressure circuits, and the like among various types of subsystems.Needless to say, an assembly process of individual subsystem isperformed before the process of assembling the various subsystems intothe exposure apparatus. When the process of assembling the varioussubsystems into the exposure apparatus is completed, a total adjustmentis performed and various kinds of accuracy as the entire exposureapparatus are secured. Incidentally, the making of the exposureapparatus is preferably performed in a clean room where the temperature,the degree of cleanliness and the like are controlled.

Incidentally, the disclosures of the PCT International Publications, theU.S. Patent Application Publications and the U.S. Patents that are citedin the description so far related to exposure apparatuses and the likeare each incorporated herein by reference.

INDUSTRIAL APPLICABILITY

As described so far, the exposure apparatus and the exposure method ofthe present invention is suitable for exposing an object. Further, thedevice manufacturing method of the present invention is suitable formanufacturing electronic devices such as semiconductor devices or liquidcrystal display devices.

The invention claimed is:
 1. An exposure apparatus that exposes asubstrate with an illumination light via a projection optical system,the apparatus comprising: a body having a metrology frame that supportsthe projection optical system; a first drive system having a firstmovable member disposed above the projection optical system and a firstmotor to drive the first movable member, the first movable memberholding a mask illuminated with the illumination light; a scale memberdisposed to be substantially parallel to a predetermined planeorthogonal to an optical axis of the projection optical system, thescale member having four sections in each of which a reflective gratingis formed and an opening that is substantially defined by the foursections, the scale member being provided at the metrology frame so thata lower end part of the projection optical system is disposed in theopening; a second drive system having a second movable member disposedbelow the projection optical system and holding the substrate and asecond motor to drive the second movable member, the second motor movingthe second movable member below the scale member so that substrate facesthe lower end part and is moved relative to the lower end part; ameasurement system having a first encoder system and a second encodersystem that measure position information of the first movable member andposition information of the second movable member, respectively, thesecond encoder system having four head groups provided at the secondmovable member so that the four head groups respectively face the foursections as the second movable member is moved, each of the four headgroups having a plurality of heads, each of the plurality of headsirradiating the reflective grating from below with a measurement beam;and a controller coupled to the first and the second drive systems andthe measurement system, the controller controlling the first and thesecond drive systems so that scanning exposure in which the mask and thesubstrate are each moved relative to the illumination light is performedfor each of a plurality of areas of the substrate in an exposureoperation of the substrate, wherein in each of the four head groups, theposition information is measured by the plurality of heads so thatdifference data of the position information is acquired in at least oneof two directions orthogonal to each other within the predeterminedplane, and in the exposure operation, the controller compensates a griderror due to grid variation caused by the reflective grating in each ofthe four sections, based on the difference data acquired in the fourhead groups.
 2. The exposure apparatus according to claim 1, wherein thecontroller compensates the grid error in a direction parallel to thepredetermined plane, in each of the four sections.
 3. The exposureapparatus according to claim 2, wherein the plurality of heads includeat least two heads that are capable of measuring the positioninformation in one of the two directions and are different in positionfrom each other in the other of the two directions.
 4. The exposureapparatus according to claim 3, wherein the plurality of heads includeat least one head that is different in position from a part of the atleast two heads or all of the at least two heads in the one of the twodirections.
 5. The exposure apparatus according to claim 3, wherein eachof the plurality of heads is capable of measuring position informationof the second movable member and measures the position information sothat the difference date of the position information is acquired, in adirection orthogonal to the predetermined plane, and the controllercompensates a grid error due to grid variation caused by the reflectivegrating in the direction orthogonal to the predetermined plane, in eachof the four sections.
 6. The exposure apparatus according to claim 5,wherein the second encoder system is capable of measuring positioninformation of the second movable member in directions of six degrees offreedom, the directions of six degrees of freedom including a firstdirection and a second direction orthogonal to each other within thepredetermined plane, and the two directions are different from the firstand the second directions at an angle of 45 degrees in a rotationaldirection within the predetermined plane.
 7. The exposure apparatusaccording to claim 1, further comprising: a detection system provided atthe metrology frame to be spaced apart from the projection opticalsystem; and another scale member, different from the scale member, thatis disposed to be substantially parallel to the predetermined plane, theanother scale member having four sections different from the foursections of the scale member and another opening, different from theopening, that is substantially defined by the four sections of theanother scale member, the another scale member being provided at themetrology frame so that the detection system is disposed in the anotheropening, a reflective grating being formed in each of the four sectionsof the another scale member, the four sections of the another scalemember being respectively faceable by the four head groups as the secondmovable member is moved, wherein position information of the secondmovable member is measured by the second encoder system in a detectionoperation of the substrate by the detection system, in each of the fourhead groups, the position information is measured by the plurality ofheads so that difference data of the position information in at leastone of the two directions is acquired, and the controller compensates agrid error due to grid variation caused by the reflective grating ineach of the four sections of the another scale member, based on thedifference data acquired in the four head groups.
 8. The exposureapparatus according to claim 7, wherein in each of the four head groups,position information of the second movable member in a directionorthogonal to the predetermined plane is measured by the plurality ofheads, and the controller compensates a grid error due to grid variationcaused by the reflective grating in the direction orthogonal to thepredetermined plane, in each of the four sections of the another scalemember.
 9. The exposure apparatus according to claim 7, wherein thescale member and the another scale member are supported in a suspendedmanner by the metrology frame so that scale member and the another scalemember are substantially disposed in a same plane.
 10. A devicemanufacturing method, comprising: exposing a substrate using theexposure apparatus according to claim 1; and developing the substratethat has been exposed.
 11. An exposure method of exposing a substratewith an illumination light via a projection optical system, the methodcomprising: holding a mask illuminated with the illumination light, witha first movable member disposed above the projection optical system;holding the substrate with a second movable member disposed below theprojection optical system, the second movable member being moved below ascale member so that substrate faces a lower end part of the projectionoptical system and is moved relative to the lower end part, the scalemember having four sections in each of which a reflective grating isformed and an opening that is substantially defined by the foursections, the scale member being disposed to be substantially parallelto a predetermined plane orthogonal to an optical axis of the projectionoptical system and provided at a metrology frame so that the lower endpart is disposed in the opening, the metrology frame supporting theprojection optical system; measuring position information of the firstmovable member and position information of the second movable member,respectively, with a first encoder system and a second encoder system,the second encoder system having four head groups provided at the secondmovable member so that the four head groups respectively face the foursections as the second movable member is moved, each of the four headgroups having a plurality of heads, each of the plurality of headsirradiating the reflective grating from below with a measurement beam;and moving the first and the second movable members so that scanningexposure in which the mask and the substrate are each moved relative tothe illumination light is performed for each of a plurality of areas ofthe substrate in an exposure operation of the substrate, wherein in eachof the four head groups, the position information is measured by theplurality of heads so that difference data of the position informationis acquired in at least one of two directions orthogonal to each otherwithin the predetermined plane, and in the exposure operation, a griderror due to grid variation caused by the reflective grating in each ofthe four sections is compensated, based on the difference data acquiredin the four head groups.
 12. The exposure method according to claim 11,wherein the grid error in a direction parallel to the predeterminedplane is compensated in each of the four sections.
 13. The exposuremethod according to claim 12, wherein each of the plurality of heads iscapable of measuring position information of the second movable memberand measures the position information so that the difference date of theposition information is acquired, in a direction orthogonal to thepredetermined plane, and a grid error due to grid variation caused bythe reflective grating in the direction orthogonal to the predeterminedplane is compensated, in each of the four sections.
 14. The exposuremethod according to claim 11, further comprising: moving the secondmovable member below another scale member, different from the scalemember, that is disposed to be substantially parallel to thepredetermined plane so that the substrate is detected by a detectionsystem provided at the metrology frame to be spaced apart from theprojection optical system, the another scale member having four sectionsdifferent from the four sections of the scale member and anotheropening, different from the opening, that is substantially defined bythe four sections of the another scale member, the another scale memberbeing provided at the metrology frame so that the detection system isdisposed in the another opening, a reflective grating being formed ineach of the four sections of the another scale member, the four sectionsof the another scale member being respectively faceable by the four headgroups as the second movable member is moved, wherein positioninformation of the second movable member is measured by the secondencoder system in a detection operation of the substrate by thedetection system, in each of the four head groups, the positioninformation is measured by the plurality of heads so that differencedata of the position information in at least one of the two directionsis acquired, and a grid error due to grid variation caused by thereflective grating is compensated in each of the four sections of theanother scale member, based on the difference data acquired in the fourhead groups.
 15. The exposure method according to claim 14, wherein ineach of the four head groups, position information of the second movablemember in a direction orthogonal to the predetermined plane can bemeasured by the plurality of heads, and a grid error due to gridvariation caused by the reflective grating in the direction orthogonalto the predetermined plane is compensated, in each of the four sectionsof the another scale member.
 16. A device manufacturing method,comprising: exposing a substrate using the exposure method according toclaim 11; and developing the substrate that has been exposed.
 17. Amaking method of an exposure apparatus that exposes a substrate with anillumination light via a projection optical system, the methodcomprising: providing a body having a metrology frame that supports theprojection optical system; providing a first drive system having a firstmovable member disposed above the projection optical system and a firstmotor to drive the first movable member, the first movable memberholding a mask illuminated with the illumination light; providing ascale member disposed to be substantially parallel to a predeterminedplane orthogonal to an optical axis of the projection optical system,the scale member having four sections in each of which a reflectivegrating is formed and an opening that is substantially defined by thefour sections, the scale member being provided at the metrology frame sothat a lower end part of the projection optical system is disposed inthe opening; providing a second drive system having a second movablemember disposed below the projection optical system and holding thesubstrate and a second motor to drive the second movable member, thesecond motor moving the second movable member below the scale member sothat substrate faces the lower end part and is moved relative to thelower end part; providing a measurement system having a first encodersystem and a second encoder system that measure position information ofthe first movable member and position information of the second movablemember, respectively, the second encoder system having four head groupsprovided at the second movable member so that the four head groupsrespectively face the four sections as the second movable member ismoved, each of the four head groups having a plurality of heads, each ofthe plurality of heads irradiating the reflective grating from belowwith a measurement beam; and providing a controller coupled to the firstand the second drive systems and the measurement system, the controllercontrolling the first and the second drive systems so that scanningexposure in which the mask and the substrate are each moved relative tothe illumination light is performed for each of a plurality of areas ofthe substrate in an exposure operation of the substrate, wherein in eachof the four head groups, the position information is measured by theplurality of heads so that difference data of the position informationis acquired in at least one of two directions orthogonal to each otherwithin the predetermined plane, and in the exposure operation, thecontroller compensates a grid error due to grid variation caused by thereflective grating in each of the four sections, based on the differencedata acquired in the four head groups.